An Assessment of Direct Restorative Material Use in Posterior Teeth by Pediatric Dentists in Canada and the

United States of America

By

Dr. Rae Elizabeth Varughese

A thesis submitted in conformity with the requirements for the degree of Masters of

Pediatric Dentistry University of Toronto

© Copyright by Dr. Rae Varughese 2015

ii

An Assessment of Direct Restorative Material Use in Posterior

Teeth by Pediatric Dentists in Canada and the United States of

America

Rae Varughese

Masters of Science with Specialization in Pediatric Dentistry

University of Toronto

2015

Abstract

Objective: To evaluate clinical decision-making related to direct restorative materials placement in

healthy, developmentally delayed (DD), and medically compromised (MC) patients.

Methods: Data was collected by a self-administered online survey by Survey Gizmo® from all active

members of the Royal College of Dentists of Canada and the American Academy of Pediatric Dentistry.

Statistical significance was set at a p value of <0.05.

Results: With a response rate of 19.3%, composite was used the most frequently for primary and

permanent Class I, II, and V restorations in healthy and MC populations. For DD, half of the time

stainless steel crowns are used for primary and amalgam for permanent Class II restorations. The majority

prefer an active role in decision-making.

Conclusions: Composite use in the healthy and MC population has greatly increased in comparison to

previous studies. In DD individuals, stainless steel crowns and amalgam is used more frequently.

iii

Acknowledgments

Over the past three years, there have been so many people who supported me while preparing

and writing this project.

I would like to express my gratitude to my co-supervisors, Dr. Paul Andrews and Dr. Michael

Sigal. Both of them have not only been great supervisors but also, mentors. I appreciate all the

time and effort you have put into my education.

Dr. Azarpazhooh went up and beyond his role as a committee member. I would like to thank him

for all the help, support, and advice he provided for this project.

I would like to thank Dr. Tanya Chacko, Dr. Amira Greiss, and Dena Taylor for their help with

editing and support during this writing process. I would especially like to thank Jeff Junkin (tech

support and making a complex graph), my ‘Living Room’ group, and Sansyrae St. Martin for

their unconditional love and support. There are so many family and friends who supported and

prayed for me; I cannot thank you all enough.

Last but definitely not least, I would like to thank my Mom, Dad, Rhea, and Robin, for their

constant love, support, and encouragement throughout my life and especially, this thesis.

~ Proverbs 16:3 (ESV) “Commit your work to the Lord, and your plans will be established”

Dr. Rae Varughese- Toronto, Canada, 2015

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Table of Contents

Acknowledgments.......................................................................................................................... iii

Table of Contents ........................................................................................................................... iv

List of Tables ................................................................................................................................ vii

List of Figures .............................................................................................................................. viii

1 Introduction .................................................................................................................................1

2 Literature Review ........................................................................................................................2

2.1 Dental Caries Burden in North America ..............................................................................2

2.2 Trends in Restorative Material Choice ................................................................................3

2.2.1 United States of America .........................................................................................3

2.2.2 Europe ......................................................................................................................5

2.2.3 Australia and New Zealand ......................................................................................7

2.2.4 Other Areas of the World .........................................................................................8

2.3 Amalgam ............................................................................................................................10

2.3.1 History of Amalgam ..............................................................................................10

2.3.2 Types of Amalgam .................................................................................................11

2.3.3 Properties of Amalgam ..........................................................................................12

2.3.4 Amalgam Longevity ..............................................................................................12

2.3.5 Amalgam Controversy ...........................................................................................15

2.3.6 Amalgam Toxicity .................................................................................................18

2.4 Tooth Coloured Restorations .............................................................................................23

2.5 Composite Resin ................................................................................................................23

2.5.1 History....................................................................................................................23

2.5.2 Composition ...........................................................................................................25

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2.5.3 Classification..........................................................................................................26

2.5.4 Polymerization Process ..........................................................................................27

2.5.5 Properties and Longevity .......................................................................................30

2.5.6 Toxicity ..................................................................................................................33

2.6 Glass Ionomer Restorations ...............................................................................................36

2.6.1 History....................................................................................................................36

2.6.2 Characteristics ........................................................................................................37

2.6.3 Fluoride Release.....................................................................................................37

2.7 Resin-Modified Glass Ionomer ..........................................................................................38

2.7.1 Setting Process .......................................................................................................39

2.7.2 Characteristics ........................................................................................................39

2.8 Compomer (Polyacid Modified Composite Resin)............................................................40

2.8.1 History....................................................................................................................40

2.8.2 Characteristics ........................................................................................................41

2.8.3 Longevity for Tooth Coloured Restorations ..........................................................42

2.9 Stainless Steel Crown ........................................................................................................45

2.9.1 Stainless Steel Crown Concerns ............................................................................46

2.9.2 Longevity ...............................................................................................................46

2.10 Rubber Dam Isolation ........................................................................................................47

2.11 Survey Tool ........................................................................................................................51

3 Objective of Thesis ...................................................................................................................53

4 Materials and Methods ..............................................................................................................54

4.1 Design ................................................................................................................................54

4.2 Survey Instrument ..............................................................................................................54

4.3 Sample Size ........................................................................................................................56

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4.4 Data Analysis .....................................................................................................................56

5 Results .......................................................................................................................................58

5.1 Descriptive Data.................................................................................................................58

5.2 Current usage of direct restorative materials .....................................................................60

5.2.1 Factors Associated with Choice of Material ..........................................................65

5.3 Rubber Dam Usage ............................................................................................................68

5.4 Dentists’ Role in Determining Restorative Material Choice .............................................70

5.4.1 Factors associated with Decision-Making .............................................................72

5.4.2 Toxicity Concern and Response ............................................................................73

6 Discussion .................................................................................................................................77

6.1 Choice of Material .............................................................................................................77

6.2 Rubber Dam Isolation ........................................................................................................83

6.3 Preference of Role in Decision-Making ............................................................................86

6.4 Survey Tool and Demographics .........................................................................................89

6.5 Limitations .........................................................................................................................90

6.6 Future Directions ...............................................................................................................91

7 Conclusions ...............................................................................................................................91

References ......................................................................................................................................92

Appendices ...................................................................................................................................117

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List of Tables

Table 2.1- Classification of Composite Resin .............................................................................. 27

Table 2.2- Success rates (%) of Primary Molar Restorations by Observation Period .................. 42

Table 5.1- Descriptive Results of Survey Participants ................................................................. 60

viii

List of Figures

Figure 2.1-The number of amalgam and resin composite restorations completed each year at the

Seoul National University Dental Hospital (Rho et al., 2013). ...................................................... 9

Figure 2.2- Restored first upper right molar of Princess Anna Ursula (d 1601) with gold and

amalgam (Czarnetzki, 1990). ........................................................................................................ 10

Figure 2.3- Survival curves of amalgam and composite restorations over a 7 year period .......... 14

Figure 2.4- Mercury vapour levels from different measurement series: cut= cutting; fil= filling;

pol= polishing; HVE= high volume evacuator; ME= mirror-evacuator; SE= saliva extractor

(Pohl & Bergman, 1995). .............................................................................................................. 22

Figure 2.5- The restoration on the primary left first maxillary molar shows a radiolucent area

under the composite resin. The arrow denotes a bubble (lack of material) on the distal surface

(Fuks et al., 2000). ........................................................................................................................ 31

Figure 2.6- The primary left first molar has a disto-occlusal composite that appears to have good

margins on the occlusal surface. After the tooth exfoliated, it exposed marginal staining and

surface defects on the proximal surface. (Fuks et al., 2000). ........................................................ 31

Figure 2.7a/b- The above figures exemplify how Vitremer, a resin-modified glass ionomer, has

the most cumulative fluoride release. In terms of daily fluoride release, all of the glass ionomers

release similar amounts of fluoride. .............................................................................................. 40

Figure 2.8- The combined survival curves from 1991, 1995, and 2000 for overall failure of five

restorative materials. ..................................................................................................................... 45

Figure 2.9- Relative importance of reasons for using rubber dam isolation (Soldani & Foley,

2007). ............................................................................................................................................ 48

Figure 5.1- Response Rates for Pediatric Dentists Web-based Survey ........................................ 59

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Figure 5.2- Restorative Material Choice for Healthy, Medically compromised (MC), and

Developmentally Delayed (DD) Patients...................................................................................... 61

1

1 Introduction

Dental caries is a multifactorial chronic infectious disease that affects approximately 50% of

children less than 12 years old worldwide (Dye, Arevalo, & Vargas, 2010). Untreated dental

caries is associated with pain, difficulty eating, poor physical growth and development, difficulty

sleeping, mood changes, learning problems, hospitalization, and in rare cases, death

(Casamassimo, Thikkurissy, Edelstein, & Maiorini, 2009; Chi, Rossitch, & Beeles, 2013). For

each carious lesion, the dental practitioner must assess which restorative material will be the

most suitable. Factors to consider when choosing the restorative material include; the

developmental status of the dentition, caries risk assessment, oral hygiene, anticipated parental

compliance, likelihood of a timely recall, and the patient’s ability to cooperate for treatment

(AAPD, 2012). The survival of dental restorations is influenced by several factors: the type of

tooth, the tooth’s position in the dental arch, the size and design of the restoration, the patient’s

age, the clinicians level of experience, and the physical properties of the restorative material

(Bernardo et al., 2007).

Since the 1880s, dental amalgam has been seen as a reliable restorative material due to its

superior mechanical properties (Christensen, 1998; Pair, Udin, & Tanbonliong, 2004). However,

there has been a decrease in the use of amalgams which may be attributed to advanced bonding

techniques of composite resins, societal mistrust towards the mercury content in amalgams,

patient preference for tooth coloured restorations, perceived greater removal of tooth structure,

and profitability for the dentist (Forss & Widstrom, 2003; Pair et al., 2004).

Within the dental literature, there is a lack of agreement between clinical and in-vitro studies on

the relative success of various restorative materials (Fuks, Araujo, Osorio, Hadani, & Pinto,

2000; Wahl, 2001; Pair et al., 2004). The lack of evidence is exemplified in the 2009 Cochrane

Review “Dental fillings for the treatment of caries in the primary dentition” where only three

studies were robust enough to be included based upon the inclusion criteria utilized (Yengopal,

Harneker, Patel, & Siegfried, 2009).

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In this era of evidence-based dentistry, high patient demands, and sensationalization by media

sources regarding the toxicity of dental materials, a fundamental knowledge and understanding

of the literature is essential to provide optimal dental care (Yengopal et al., 2009). This study

will determine practitioner choice of restorative material for primary and permanent molars in a

variety of clinical scenarios, the criteria utilized in making the choice, rubber dam usage, and the

preferred role of pediatric dentists in decision making.

2 Literature Review

2.1 Dental Caries Burden in North America

Over the past 50 years, there have been improvements in dental caries prevalence; however,

dental caries continues to be the “most common chronic disease of childhood in the United

States” (Services, 2000; Dye et al., 2010). The Fourth National Health and Nutrition

Examination Survey (NHANES 1999-2004) in the United States of America (US) reported the

dental caries prevalence in the primary dentition for 2-5 year olds to be 28%, in the mixed

dentition for 6-8 year olds to be 52-53%, and in the permanent dentition for 12-15 year olds to be

51% (Dye et al., 2010). Between the third (1988-1994) and the fourth NHANES (1999-2004)

studies, the caries prevalence increased in the primary dentition from 24% to 28% for 2-5 year

olds (Dye et al., 2010). Preschoolers from low-income families were found to have about three

times more untreated caries in comparison to higher income families (CDC, 2013).

The trends in Canada follow the findings in the US. According to the Oral Health Component of

the Canadian Health Measures Survey 2007-2009, 57% of 6-11 year olds have or have had a

cavity (CHMS, 2007-2009). The Canadian Institute of Health Information reports that 31% of all

out- patient pediatric surgical operations for children age one to five are to treat dental caries

(CIHI, 2013). The public cost associated with these day surgeries is $21.2 million per year;

however, this is only a small percentage of the cost as it does not include the cost of the health

care providers or anesthesiologists (CIHI, 2013). Overall, the burden of dental disease in the

pediatric population is significant, therefore, the selection of the most cost effective restorations

is imperative.

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2.2 Trends in Restorative Material Choice

Geographically, the predominant type of restorative material varies mainly due to changing

public opinions on restorative materials and governing body recommendations.

2.2.1 United States of America

In the United States of America (US), restorative material choice has historically varied based

upon geography. Guelmann and Mjor (2002) surveyed the active members of the American

Academy of Pediatric Dentistry in Florida. With a 70% return rate, they found that resin-based

materials were the most commonly selected for Class I (59%) and II (46%) restorations in

primary molars. Amalgam was only chosen by 20% for Class I and 28% for Class II restorations.

If three or more surfaces were involved, stainless steel crowns (SSC) were used. Over a third

reported that they have amalgam free offices. Female dentists tended to use more resin-based

materials for posterior restorations than amalgam.

In 2004, another survey was completed in California about the use of restorative materials for

specifically Class II restorations in primary molars (Pair et al., 2004). The survey not only

included the pediatric dentist’s preferred choice of material to restore Class II carious lesions but

also; the indications and contraindications affecting the use of materials, techniques used to place

the restorations, role of the dental literature in decision making, and demographic information

about the dentist. With a 66% response rate, amalgam was most frequently selected (57%),

followed by composite (29%), compomer (6%), and glass ionomer/resin-modified glass ionomer

(5%). No significant trend could be seen between the restorative material of choice for Class II

restorations in primary teeth and the number of years practicing and average number of patients

treated per day. Amalgam was significantly chosen more often with HMO, Denti-Cal, and

Healthy families (P=0.002) insurance than esthetic restorations. Of the 23% of respondents who

described the use of amalgam as “non-routine”, the reasons for using amalgam include; lack of

insurance coverage for non-amalgam restorations (69%), poor isolation (57%), poor patient

cooperation (46%), poor oral hygiene (33%), subgingival preparation margins (28%),

preparation margins in cementum (24%), and excessively large preparations (24%). The reported

reasons for selecting amalgam included greater longevity, superior mechanical properties,

requires less time to place, less patient cooperation needed, and is more affordable (Pair et al.,

4

2004). About a third of the respondents use composite resin 50% of the time for Class II

restorations with the main reasons being patient preference (86%) and better esthetics (78%).

Only a quarter of the respondents felt that it has better longevity and superior mechanical

properties and that its usage is evidence based/supported by research. Concern about the toxicity

of amalgam was the reason for choosing composite for 9% of the respondents. Glass

ionomer/RMGI is used less than 25% of the time for 88% of the respondents while 38% felt

there were no indications for the use of GI/RMGI for Class II lesions in primary teeth. Three

quarters of the respondents felt that the role of the literature has a major but not the primary role

in selection of restorative materials.

Zimmerman, Feigal, Till, and Hodges (2009) used a postal survey to assess restorative material

preferences by dentists across the USA. Of the sampled pediatric dentists, 41% used amalgam

routinely and 20% never used amalgam. A strong association with mercury concerns and

socioeconomic status (SES) was found; as the SES of the parent increased, the concern for

mercury toxicity also increased. Only 38% of pediatric dentists chose to restore ideal Class II

lesions with amalgam while 58% chose a tooth coloured material such as composite, compomer,

or resin-modified glass ionomer. For large interproximal caries, 76% chose SSC as the preferred

material (Zimmerman et al., 2009).

A nationwide survey of general dentists and specialists, including 4% pediatric dentists, was

conducted regarding the types of restorations that dentists selected for the restoration of their

own teeth (Rosenstiel, Land, & Rashid, 2004). Regardless of the graduation date of the dentist,

the predominant restoration in the dentists’ own mouths was amalgam (Rosenstiel et al., 2004).

The majority of amalgam restorations were over 10 years old while most direct and indirect

composite resin restorations were less than 10 years old.

There has been a pronounced shift towards tooth coloured restorations in the United States

(Berthold, 2002; Mitchell, Koike, & Okabe, 2007). Between 1990 and 1999, the number of

composite resin restorations increased from 13 million to 46 million per year (Berthold, 2002;

Mitchell et al., 2007). More research is necessary to assess the current use of tooth coloured

restorations.

5

2.2.2 Europe

In parts of Europe, there has been a move to a “post amalgam era” in the pediatric population

(Forss & Widstrom, 2003). An increase in the use of composite resin has been noted in Norway,

Finland, Germany, Italy, and Denmark for Class III, IV, and V restorations (Sunnegardh-

Gronberg, van Dijken, Funegard, Lindberg, & Nilsson, 2009).

In Belgium, a national survey was administered in 1983 and again in 1988 to assess the types of

restorative materials used for proximal lesions. In 1983, amalgam was preferred most frequently

at 59% but dropped significantly to 20% in 1988 (Van Meerbeek, Vanherle, Lesaffre, Braem, &

Lambrechts, 1991). In addition, the technique for placing composite resin changed significantly

as well. In 1983, 18% of dentists seldom used acid etching for placing composite resins but in

1988, 69% reported using acid etching. There was a correlation with older dentists more

frequently placing composite resins without acid etching but it was not statistically significant.

Another significant finding was that in 1983, 66% of practitioners never used composite resin for

Class II restorations while 5 years later, this percentage dropped to 15%.

In Finland, the use of amalgam for children dramatically decreased in the 1990s (Forss &

Widstrom, 2003). In 1994, GIC was being used for 47% of permanent tooth restorations in

children (Widstrom & Forss, 1994). This trend decreased to 40% among children and 19%

among adults in 1997 and in 2003, the most common restorative material to restore primary

molars was resin-modified glass ionomer (8-57%) (Forss & Widstrom, 2001, 2003). For the

primary dentition, amalgam was never used (Forss & Widstrom, 2003). In another study by the

same authors, in patients older than 17 years old, composite was used the most often (74.9%) and

resin-modified glass ionomer and amalgam were seldom used (Forss & Widstrom, 2001).

Additionally, in 1987-88, 6% of all tooth-coloured restorations, mainly Class II restorations in

primary teeth, were GIC (Qvist, Qvist, & Mjor, 1990). GIC increased in popularity until it

attained its highest rates in Finland and Norway at approximately 25% (Mjor, Dahl, &

Moorhead, 2002). In 1996, a survey of general dentists in Norway found that 85% of all

restorations placed in children were tooth coloured restorations with the majority being glass

ionomer or resin modified glass ionomers (Mjor et al., 2002). In a second survey in 2001 at 10

randomly selected public dental clinics; 46% of all restorations were glass ionomer or resin-

6

modified glass ionomer, 38% were compomers, 5% was amalgam, 2% was composite, and 9%

were other. To assess material longevity, the new restorations placed in 1996 were reassessed;

the median longevity for amalgam restorations in primary teeth was 3 years while tooth coloured

restorations was 2 years (Mjor et al., 2002). The paper alludes that the restorations were assessed

in December 2000- January 2001 but the follow-up time is unclear. In addition, it is not clearly

stated how many restorations were lost to follow-up. In a study assessing 4030 Class II

restorations by 27 general dentists in the Public Dental Health Service from 2001-2004;

composite was used 81.5% of the time, compomer at 12.7%, amalgam at 4.6%, and glass

ionomer at 1.2% (Vidnes-Kopperud, Tveit, Gaarden, Sandvik, & Espelid, 2009). Amalgam was

more often used; in treatment of patients with a higher reported decayed-missing-filled teeth

(DMFT), in deep caries (9.1%) versus shallow caries (2.9%), and in molars (8.1%) rather than

premolars (1.5%) (Vidnes-Kopperud et al., 2009). In 2002, the Norwegian Directorate of Health

reported that composite is the preferred restoration for general dentists and the proportion of

amalgam restorations for children was reduced by about 90% since 1995 (Skjelvik, 2012). A

2006/07 report about Norway’s chemical policy by the Norwegian Ministry of the Environment

called for a reduction in mercury and mercury products (Environment, 2006-2007). The

perceived toxicity of amalgam was secondary to the concern regarding the environmental impact

of mercury.

In Sweden, researchers found that the majority (93%) of all new restorations were restored with

composite resin (Espelid, Tveit, Mejare, Sundberg, & Hallonsten, 2001; Sunnegardh-Gronberg et

al., 2009). Whereas in 2001, only 2.9% of Swedish dentists used amalgam to restore primary

occlusal caries while there was a more positive response for use of amalgam in Norway at 19.9%

and Denmark at 52.4% (Espelid et al., 2001). When restoring with amalgam, a traditional Class

II preparation was most commonly used in contrast to a tunnel preparation for glass ionomer

restorations and a saucer shaped cavity design for composite resins (Sundberg, Mejare, Espelid,

& Tveit, 2000). Both the tunnel and saucer shaped cavity designs have a higher failure rate than

traditional Class II restorations as many of the studies claiming a higher success rate have

unacceptable success criteria and short follow-up times that inflate the reported success rate

(Nordbo, Leirskar, & von der Fehr, 1998; Horsted-Bindslev, Heyde-Petersen, Simonsen, &

Baelum, 2005). Due to environmental concerns, Sweden and Denmark followed Norway and

7

banned the use of mercury in dental amalgam effectively banning the use of amalgam in April

2008 (Nyheter, 2007; Reuters, 2008).

In a survey of general dentists in Croatia, 66% chose composite resin as the preferred material

for proximal caries (Baraba, Domejean-Orliaguet, Espelid, Tveit, & Miletic, 2010). Of these

dentists, 46% preferred tunnel preparations versus traditional Class II or saucer type

preparations. There was a significant relationship with dentists younger than 45 years old

preferring tunnel preparations while older respondents preferred traditional Class II preparations

(p= 0.017).

2.2.3 Australia and New Zealand

Amalgam use in Australia has steadily declined from 57.9% in 1983/84 to 27% in 1997/98 for all

restorations (Policy, 1999; Tran & Messer, 2003). In 2003, a national survey of the members of

the Australasian Academy of Paediatric Dentistry and the Australian and New Zealand Society

of Pediatric Dentistry examined restorative material choice (Tran & Messer, 2003). This 3-part

29-item survey had a 74% return rate. The factors considered when making material choices for

vital primary teeth included; patient age, behavior, caries experience, moisture control,

restoration retention, oral hygiene/plaque control, and parental motivation. Tooth coloured

restorations were chosen for moderate-sized Class I and II restorations in primary molars by 92%

and 84% of respondents. If there were two separate proximal lesions in a primary molar; 51%

chose a stainless steel crown, followed by 14% for compomer, and 9% for amalgam or glass

ionomer cement. If child behavior and moisture control were issues, the majority of survey

respondents chose a glass ionomer restoration, reporting their belief that it is adhesive to dentin

even when contaminated by saliva. In addition, the younger respondents (between 21-40 years)

were more likely to choose tooth coloured restorations compared to the older dentists. If the child

was younger or had a high caries risk, amalgam and/or a stainless steel crown was chosen most

often. In addition, Tyas (2005) found that composite resin was used twice as frequently as

amalgam and almost four times as often as a glass ionomer restoration.

8

However, Burke et al. (2004) found that composite resin was used; always by 12%, often by

29%, and sometimes by 32% for large extensive, occlusal bearing posterior restorations. The

main determinants for choosing composite resin were; aesthetic demands (99% of respondents),

parental preferences (96%), patients’ financial situation (82%), and lecturers’ suggestions (72%)

(Burke et al., 2004). A speculation by these authors about the increased use of tooth coloured

materials was that there is a general trend of declining caries experience and increased access to

care, thus allowing smaller carious lesions to be detected. If carious lesions are detected early,

the caries may be more amenable for composite resin use (Tran & Messer, 2003). However, this

may actually be a geographic trend to over treatment due to an over saturation of dentists as

these claims are not supported by the literature (Caldwell, 2014a, 2014b). A review of the current

literature reports an increasing trend for caries in the pediatric population (Australian Research

Center for Population Oral Health, 2004; Health, 2011).

2.2.4 Other Areas of the World

A retrospective cross-sectional clinical study conducted at the Seoul National University Dental

Hospital assessed the longevity of amalgam and composite restorations in the posterior dentition

(Rho, Namgung, Jin, Lim, & Cho, 2013). The restorations were placed by students for all ages of

patients. This study showed that amalgam was predominantly used until the early 2000s where a

marked increase in the use of composite occurred (Figure 2.1). At the time of publication, the

restoration used most often is composite. Interestingly, since the use of composite has gained

popularity, the number of restorations placed per year has dramatically increased (Figure 2.1).

9

Figure 2.1-The number of amalgam and resin composite restorations completed each year

at the Seoul National University Dental Hospital (Rho et al., 2013).

Apart from the Atraumatic Restorative Technique (ART) which is not discussed in this study,

there are a limited number of studies that have been reported on direct restorative material use in

other countries. The literature search only included papers published in English; therefore, there

could be more studies that were not identified. Japan and Jordan have both reported direct

restorative material use in the early 2000s. At the Pediatric Dentistry Department in the Tokyo

Dental College; metal inlays were placed in 29.4% of the posterior deciduous teeth restored,

composite resins in 27.2%, stainless steel crowns in 25.7%, glass ionomer restorations in 6.6%,

and amalgam restorations in 3.4 % (Fukuyama, Oda, Yamashita, Sekiguchi, & Yakushiji, 2008).

Amalgam is seldom used in general practice in Japan. This could be due to the fear of mercury

toxicity after the poisoning of the inhabitants of Minamata and Niigata due to methyl mercury-

contaminated fish in the mid-1950s (Harada, 1995; Fukuyama et al., 2008). In Jordan, a survey

of 241 general dentists showed that dental amalgam was used for 88.8% of all Class I and Class

II restorations (AlNegrish, 2001, 2002). Due to the limited literature in English about material

usage, the trend in Europe and North America to move towards composite and tooth coloured

restorations cannot necessarily be generalized to the rest of the world.

10

2.3 Amalgam

2.3.1 History of Amalgam

Dental amalgam is a metallic restorative material used for direct filling of carious lesions

(Czarnetzki, 1990). The first use of amalgam for dentistry is not well established; however, there

have been reports as early as 659 AD of a silver paste used to restore teeth in China (Czarnetzki,

1990). One of the earliest dental records is from 1601 which show a mixture of amalgam and

gold restorations (Figure 2.2).

Figure 2.2- Restored first upper right molar of Princess Anna Ursula (d 1601) with gold

and amalgam (Czarnetzki, 1990).

In 1603, the process of creating an amalgam restoration was described by Tobias Dorn Kreilius

(Czarnetzki, 1990; Nicolae, 2010). This process involved dissolving copper sulphide with strong

acids, adding mercury, bringing it to a boil, and then pouring it onto a tooth. Louis Regnart, now

described as the “Father of Amalgam”, was able to create a solid mixture by adding mercury

which lowered the melting temperature significantly (Czarnetzki, 1990; Nicolae, 2010). Dental

amalgam was reported to be used as a restorative material in England in 1819 and in France in

1826 (Eley, 1997).

11

2.3.2 Types of Amalgam

Dental amalgam is an alloy of silver, copper, tin, and zinc combined with metallic mercury

(Fuks, 2005; Clarkson & Magos, 2006). These particles combine with mercury to form a 2-phase

matrix:

Gamma 1- binding of silver and mercury (Ag2Hg3);

Gamma 2- binding of tin and mercury (Sn7Hg).

Unreacted alloy particles create the gamma 2 phase, which is responsible for early fracture and

failure of restorations; thus, copper was increased to replace the tin-mercury phase with a

copper- tin phase (Cu5Sn5). This matrix decreases the corrosion of tin, thereby strengthening the

restoration (Donly, Segura, Kanellis, & Erickson, 1999; Fuks, 2002).

There are two main types of amalgam:

a conventional silver-tin amalgam made from a silver-tin alloy with small amounts of

copper and zinc and

high copper amalgam (13-20% copper) made from an admixed alloy (mixture of silver-

tin and silver-copper) or from a single alloy (ternary silver-copper-tin) (Berry, Nicholson,

& Troendle, 1994; Eley, 1997).

Corrosion occurs when a metal reacts with a non-metallic element by an oxidation reduction

reaction (Eley, 1997). The fluid electrolyte of saliva allows the positive metal ions to enter

solution and release free electrons. In low copper amalgam, the gamma 2 phase creates the

marginal seal; since there is no gamma 2 phase in high copper amalgam restorations, double the

amount of time is required to produce a similar seal (Ben-Amar, Cardash, & Judes, 1995; Fuks,

2002, 2005). The self-sealing properties of amalgam decrease the chance of microleakage,

thereby protecting the pulp and dentin. The use of varnish in high copper amalgams maintains

the seal until the corrosion products achieve its own self-seal. By adding more copper, the

amount of mercury is decreased in the alloy.

In Canada, the liquid mercury (Hg) and alloy are packaged separately in sealed single use

capsules (Richardson, 1995). Prior to use, they are combined using an amalgamator. The

12

material becomes a metallic soft paste which can be placed into a cavity preparation with the

initial set occurring within 30 minutes (Richardson, 1995). Capsulation has greatly reduced the

amount of exposure to mercury for both the dental team and the patient.

2.3.3 Properties of Amalgam

Dental amalgam restorations provide advantages over other dental restorative materials as they

can be placed quickly in a relatively wet field while still maintaining high strength, durability,

longevity and marginal integrity (Bernardo et al., 2007; Soncini, Maserejian, Trachtenberg,

Tavares, & Hayes, 2007). Amalgam placement is not as technique sensitive when compared to

composite resins which require strict saliva and moisture control. Moisture contamination can

cause delayed expansion especially in zinc containing alloys (Donly et al., 1999; Fuks, 2002). To

achieve maximum success, amalgam restorations require adequate retention as outlined by the

principles by G.V. Black. Some common errors in cavity design which weaken the restoration

include over-flaring of proximal outlines, leaving flash on the margins, narrow isthmus width,

and excessive tooth reduction (Fuks, 2005). Since amalgam retention necessitates a larger

preparation, some authors recommend a conservative resin restoration with a sealant for small

Class I restorations (Affairs, 1998; Fuks, 2002). In addition, the mercury and silver components

in the amalgam also provide bacteriostatic properties which aid in patients who have poor oral

hygiene (Morton, North, & Engley, 1948; Morrier et al., 1998; Silver, 2003; Bates, Fawcett,

Garrett, Cutress, & Kjellstrom, 2004; Roberts et al., 2008; Busscher, Rinastiti, Siswomihardjo, &

van der Mei, 2010). Overall, amalgam is a good restorative material for small to moderate sized

interproximal lesions.

2.3.4 Amalgam Longevity

The longevity of amalgam restorations has been studied directly and as a control for composite,

resin-modified glass ionomer, compomer, and stainless steel crown. The main reasons for failure

include secondary caries and fracture/loss of the restoration (Mjor, 1997; Hickel et al., 2005;

Shenoy, 2008). Since it is not technique sensitive, the failures secondary to operator error and

13

insufficient marginal adaptation are minimal. With the increase in copper, amalgam now has a

higher survival rate than the conventional amalgam (Letzel, van 't Hof, Vrijhoef, Marshall, &

Marshall, 1989; Shenoy, 2008). Between the two primary molars, first molars have a higher

failure rate (Holland, Walls, Wallwork, & Murray, 1986; Hickel et al., 2005; Kilpatrick &

Neumann, 2007). Most amalgam failures occur between the first and second year after placement

(Ostlund, Moller, & Koch, 1992).

The annual failure rates from the literature reviewed ranged from 0% to 37.2% for Class II

restorations (Hickel et al., 2005; Kilpatrick & Neumann, 2007). The studies with the higher

annual failure rates were retrospective studies with treatment that was performed by either

undergraduate or graduate students (Hickel et al., 2005).

Roberts and Sherriff (1990) published a well-designed study about amalgam which had very low

failure rates. Primary molar Class I amalgam restorations had a failure rate of 3.9% with an

estimated survival time greater than 8.5 years. For Class II restorations, the failure rate was

11.6% with an estimated survival time of 7.5 years. For permanent molars, the failure rate for

Class I and II restorations was 6.5% and 8%, respectively (Roberts & Sherriff, 1990). The low

failure rates may be due to case selection, extensive use of rubber dam isolation, and that all

dentists participating were specialists (Roberts & Sherriff, 1990).

A literature review by Kilpatrick and Neumann (2007) found that the failure rate of amalgam

was difficult to assess due to the lack of “Grade A” studies in a variety of settings. The Danish

Public Dental Service was reported to have the most clinically reliable study due to the size of

the study (n >1000), number of operators (n=14), and the duration of follow-up (96 months)

(Qvist, Laurberg, Poulsen, & Teglers, 2004; Kilpatrick & Neumann, 2007). The median survival

time for amalgam was 7.5 years while GIC was 42 months.

Bernardo et al. (2007), reported 94.4% of all amalgam restorations survived for 7 years when

placed in posterior permanent molars of children aged 8-12 years old. The survival of composite

was lower with a rate of 85.5% over the 7 year follow-up. For small (less than a quarter of total

surface area) and one surface amalgam restorations, there was a survival rate of 99%. Secondary

caries was the main reason for failure in both amalgam (66%) and composite (88%) restorations

independent of; arch, tooth type, number of restorations needed in one patient, and restoration

14

size. The risk of secondary caries was 3.5 times greater in composite than in amalgam

restorations; however, the risk of fracture for composite was 0.9 times lower than amalgam

(Figure 2.3). A major limitation of the study is that the follow up rates are not reported.

Figure 2.3- Survival curves of amalgam and composite restorations over a 7 year period

(Bernardo et al., 2007)

Levering and Messer (1988) retrospectively reviewed 226 pediatric dental patient charts, at a

school clinic. The variability in success rate based on age of the patient was assessed. In children

over 7 years old, amalgam success rates for Class I were 92% with a mean of 43.3 months and

87% for Class II restorations with a mean of 38.6 months. In comparison, for 4-7 year old

patients, the success rate for Class I amalgams was 60% and for Class II amalgams was 74%.

However, the selection in this study may be biased as only the records of children with amalgam

in at least 4 primary molars were included. These amalgam restorations may not be

representative of children with a lower caries risk; therefore, these results are specific to a high

caries risk population. Based on the literature to date, the greatest success rates for smaller caries

is with amalgam and for larger caries is stainless steel crowns in the primary posterior dentition

(Levering & Messer, 1988; Papathanasiou, Curzon, & Fairpo, 1994; Berg, 1998; Fuks, 2005;

Hickel et al., 2005; Soncini et al., 2007; Kovarik, 2009).

In a cross-sectional clinical study across all ages at a Korean dental school, the median survival

time of amalgam and composite were 8.7 and 5.0 years, respectively (Rho et al., 2013). The most

common reasons for failure of amalgam restorations were loss (36.4%), fracture (27.3%), and

secondary caries (21.2%) while composite resins were secondary caries (21.2%), loss of

15

retention (23.8%), and fracture (14.3%). Although this study was done in a University setting,

amalgam restorations completed by students had a higher median survival time (13.3 years

[10.0-15.5]) than residents (8.3 yr [3.9-13.7]) or professors (8.1 yr [3.9-13.7]).

Recently, a Cochrane review compared direct composite resin fillings to amalgam for permanent

or adult posterior teeth which reinforced the benefit of amalgam restorations (Rasines Alcaraz et

al., 2014). With seven trials that have a minimum of a 5 year follow-up included in the

systematic review, it was found that resin restorations had a significantly higher risk of failure

than amalgam restorations and risk of secondary caries. There was no evidence of an increased

risk of restoration fracture. This meta-analysis included only two studies that had restorations

done in 921 children.

2.3.5 Amalgam Controversy

2.3.5.1 History

In 1834, amalgam was introduced in the US by the Crawcour Brothers. However, they produced

a grossly unsatisfactory product which led to a resolution by the American Society of Dental

Surgeons in 1845 to declare the use of amalgam as malpractice (Mackert, 1991; Eley, 1997).

Any member who refused to sign was at risk of expulsion. The ban spawned a number of

investigations regarding the composition and properties of amalgam in the US, United Kingdom,

and France. As a result of the findings the policy was reconsidered in 1850, allowing for the

gradual acceptance of amalgam as a useful restorative material. The appropriate use of amalgam

was promoted by G. V. Black in 1891 (Mackert, 1991; Joseph, 2005).

Between 1926-28, the second debate on amalgam was started by Dr. Alfred Stock, a Professor of

Chemistry at Kaiser-Wilhelm Institute in Germany (Stock, 1971a, 1971b). After 25 years of

direct contact with mercury in his laboratory Dr. Stock suffered from mercury poisoning. At that

time, low copper-silver-tin amalgam was supplied in a tablet form which required heating on an

iron spoon until mercury appeared. The amalgam was then transferred to a mortar and pestle

where it was triturated into a soft paste; thus, it was likely to release significant quantities of

mercury vapour (Eley, 1997). In 1930, a committee from the medical department of the Charité

16

Hospital in Berlin declared that there was no science to condemn silver-tin amalgam restorations

that were in use at that time (Eley, 1997). In a 1941 lecture in Sweden, Stock disassociated

himself from the anti-amalgam group by reporting that “rare cases of mercury poisoning [due to]

mercury vapour from low copper-silver-tin amalgam should in no way affect the further use of

silver amalgam in dental practice” (Eley, 1997).

In the 1990s, Dr. H.A. Huggins started an anti-amalgam campaign based on the claims of Dr.

Olympio Pinto of Rio de Janeiro, Brazil, who believed that the effects of amalgam could range

from leukemia to bowel disorders (Eley, 1997; Huggins, 2007). He wrote a book titled “It’s All

in Your Head” where he claimed that the mercury component could cause damage to DNA and

rupture cell membranes causing diseases like seizures, multiple sclerosis, and leukemia

(Huggins, 2007). As a result, a survey was conducted in 1995 that showed that 23% of the 8143

dentists surveyed were concerned about amalgam secondary to the mercury content in the United

States (Christensen, 1996).

2.3.5.2 Sources of Mercury

Mercury (Hg) is a rare chemical element from the Earth’s crust. It has a boiling point of 357

degrees Celsius, a melting point of -39 degrees Celsius and is insoluble in water (Clarkson &

Magos, 2006). In comparison to other metals, mercury is a poor conductor of heat but is a fair

conductor of electricity (Clarkson & Magos, 2006).

Mercury occurs naturally in several forms: elemental metal mercury (Hg0), inorganic mercury

(ionic salt forms, Hg2+

), and organic mercury compounds such as methyl mercury, ethyl

mercury, and phenyl mercury (Clarkson & Magos, 2006). Half of the environmental mercury

comes from natural sources such as volcanic activity, geothermal vents, forest fires,

volatilization from the ocean, flooding, and natural weathering processes of mercury-bearing

rocks (Canada, 2007). About 2 million kilograms per year of mercury is deposited from the

atmosphere into the oceans (Jones, 1999). In addition, the combustion of fossil fuels contributes

to about 42% of the environmental mercury pollution while medical waste is only 5% (Jones,

1999).

17

In Canada, there is a discrepancy about the total environmental mercury pollution due to dental

restorations (Nicolae, 2010). According to dental researchers, 33 metric tons of mercury is

released yearly which is 0.1% of the total annual global mercury pollution. However, the United

Nations Environmental Program’s (UNEP) Governing Council has stated the global annual

mercury release is about 10x higher (from 260 to 340 metric tons), which is about 1% of the

worldwide total pollution (Nicolae, 2010). This gross discrepancy makes it difficult to ascertain

the impact that dentistry has on worldwide mercury pollution.

Mercury exposure occurs from a wide variety of sources including; soil, water, air, food as well

as dental amalgam (Canada, 2007). Methyl mercury can be formed from inorganic mercury by

anaerobic organisms that live in lakes, rivers, wetlands, sediment, soil, and the ocean. Bio

magnification can occur as methyl mercury moves up the food chain from bacteria to plankton to

herbivorous fish to fish-eating fish. As it moves up, the concentration of methyl mercury in the

organism increases, causing a significant source of human methyl mercury exposure (Canada,

2004). The Canadian Food Inspection Agency (CFIA) regularly tests commercial fish and

shellfish with the recommendation from Health Canada of only 0.5ppm mercury in commercial

fish (Canada, 2007). In the US, the Hg level was investigated in 231 different food stuffs

(Richardson, 1995). With a detection rate limit of 0.001 µg Hg/g, it was found that ice cream

may contain up to 0.023 µg Hg/g, eggs up to 0.012 µg Hg/g, spinach and poultry up to 0.011 µg

Hg/g, boiled broccoli up to 0.004 µg Hg/g, and boiled cauliflower 0.021 µg Hg/g (Richardson,

1995). Other potential sources of mercury exposure include cosmetics, skin whitening products,

and some types of jewelry (Goldman, Shannon, & American Academy of Pediatrics: Committee

on Environmental, 2001; Canada, 2004). In 2008, Minnesota became the first US state to ban

intentionally added mercury in cosmetics (Nicolae, 2010). Exposure to organic mercury from

food results in absorption six times greater than inorganic or ionic mercury which is found in

amalgam (Jones, 1999).

Mercury is released from dental amalgam in several ways including chewing, tooth brushing,

and ingestion of hot foods/liquids (Richardson, 1995). Despite encapsulating the silver-tin alloy,

there are still concerns about the effects of inhalation of mercury vapour, ingestion of amalgam,

allergy to mercury, and environmental burden (Fuks, 2005). Currently, there is no indication of

any ill- health effects secondary to mercury at levels below 5µg Hg/g creatinine or 7 µg Hg/L in

18

urine (Nicolae, Ames, & Quinonez, 2013). For the majority of individuals in Canada and the US,

the estimated mercury exposure from dental amalgam, regardless of the number of surfaces

restored, is significantly lower than the values estimated to cause health risks (Nicolae et al.,

2013; WHO, Geneva, 2003). For the overwhelming majority of people, there are no harmful

effects known to be caused by the average levels of mercury exposure from amalgam

restorations (Canada, 2004; Nicolae et al., 2013). Health Canada estimates that for the average

20-59 year old Canadian, the amount of mercury absorbed by the body is 9 millionths of a gram

per day with amalgam accounting for only 3 millionths of a gram per day (Canada, 2004).

Chewing produces 1.2µg of ingested mercury per adult every day (Fuks, 2005). For a newborn

child and mother, the amount of fish consumed had a stronger correlation than the number of

amalgam restorations when assessing mercury levels (Eley, 1997; Fuks, 2002).

When an amalgam is inserted, low levels of ionic and elemental mercury vapours are released

and this rate of release decreases with time (Lyttle & Bowden, 1993). To quantify the amount of

mercury released during chewing, prepared Class I amalgam restorations in extracted human

molars were placed in a bi-axial hydraulic mechanical system (Berdouses et al., 1995). After 30

days, a 90% decrease in mercury release was seen in two different types of amalgam. According

to the results, a single surface occlusal amalgam releases a steady state amount of 0.03 µg

Hg/day (Berdouses et al., 1995). It is speculated that the passive tarnish layer which develops

over time causes the resistance of mercury release from aged amalgam. Several in-vitro studies

showed that Streptococcus mutans biofilms facilitated the release of mercury from newly

inserted amalgam but after two years, mercury was not released (Lyttle & Bowden, 1993).

2.3.6 Amalgam Toxicity

2.3.6.1 Health Effects

One of the reasons for the shift away from amalgam is due to mercury and its perceived toxicity.

Thus, the effect of mercury on the kidney, brain, and immune function has been widely studied.

The main ways for mercury to be excreted from the human body is through urine or feces (Fuks,

2002; Levy et al., 2004). In multiple studies, the mean urinary concentrations of mercury are

19

statistically significantly higher than prior to restoration placement; however, no adverse health

effects were found (Khordi-Mood, Sarraf-Shirazi, & Balali-Mood, 2001; Bellinger et al., 2006;

DeRouen et al., 2006; Bellinger, Daniel, Trachtenberg, Tavares, & McKinlay, 2007; Barregard,

Trachtenberg, & McKinlay, 2008; Shenker, Maserejian, Zhang, & McKinlay, 2008; Surkan et

al., 2009)

Historically, military groups were used to study the toxic effects of amalgam. In an Air Force

Health Study, 1663 dentate Vietnam era veterans were assessed for clinical neurological signs,

vibrotactile thresholds, and peripheral neuropathy. No significant associations were found

between amalgam exposure and clinical neurological signs of abnormal tremor, coordination,

station or gait, strength, sensation, or muscle stretch reflexes (Kingman, Albers, Arezzo,

Garabrant, & Michalek, 2005). The only significant associations were between amalgam

exposure and the continuous vibrotactile sensation response; however, these findings were

considered to be sub-clinical and had no effect on quality of health. A retrospective cohort study

of 20,000 people in the New Zealand Defense Force showed no significant association between

chronic fatigue syndrome or kidney disease as well as minimal evidence for Alzheimer or

Parkinson’s disease (Bates et al., 2004).

In children who had both amalgam and composite restorations, there were no statistically

significant differences in neuropsychological, psychosocial, and renal function over a five year

period (Bellinger et al., 2006; Bellinger et al., 2007; Bellinger et al., 2008). In addition, there

were no statistically significant differences in measures of memory attention, visuomotor

function, nerve conduction velocities, or other neurological outcomes between amalgam and

composite groups (DeRouen et al., 2006; Lauterbach et al., 2008).

Through autopsies, it was found that the concentration of methyl mercury in the brain can be

calculated using the amount of methyl mercury in the blood (Bjorkman et al., 2007). It is

postulated by that the number of dental amalgam surfaces is an indicator of the concentration of

the inorganic mercury within the brain. In the Casa Pia Children’s Dental Amalgam Trial,

porphyrin was used to assess mercury exposure; there were increases in penta-, precopro-, and

coproporphyrins but these increases were not statistically significant (Woods et al., 2009).

20

Shenker et al (2008) evaluated how mercury from dental amalgams could affect immune

functioning in children. Although this was a novel study, it is considered only exploratory as the

sample size was very small. However, there was no difference in B and T lymphocyte,

monocyte, and neutrophil distribution in the blood (Shenker et al., 2008). In addition, no

significant differences were found between composite and amalgam groups for mercury resistant

bacteria (Roberts et al., 2008).

Children from the Childhood Autism Risk from Genetics and the Environment (CHARGE)

Study were evaluated for blood Hg concentrations and autism spectrum disorder (ASD) (Hertz-

Picciotto, 2010). Fish consumption predicted the total Hg concentration in both the age matched

control and the ASD children. After adjustment, the levels of Hg in the blood were similar

between the two groups, thereby showing that mercury does not have a direct effect on autism.

Geier, King, Sykes, and Geier (2008) published a selective review of the literature and reported

that the evidence showed an association between mercury and autism spectrum disorder.

However, they did not disclose that they profit financially by providing “expert” testimony for

parents during litigation about thimerosal in pediatric vaccines. The July 2009 Amalgam Safety

Update by the American Dental Association report state that “his testimony is merely subjective

belief and unsupported speculation” as well as “intellectually dishonest”(Affairs, 2010).

Correlations between multiple sclerosis and amalgam have been made; however, there is not a

statistically significant association (Craelius, 1978; Ingalls, 1986; Aminzadeh & Etminan, 2007).

Some studies have reported an increased odds ratio for multiple sclerosis but there were limited

exposure measures and a small number of subjects (Bates et al., 2004; Aminzadeh & Etminan,

2007). Authors have called for increased investigation to determine the effect of dental amalgam

on multiple sclerosis.

When assessing in-utero exposure, there is no evidence that elemental Hg causes adverse

pregnancy problems or health effects on the child. The number and surface area of amalgam

restorations increases the Hg concentration in the amniotic fluid and umbilical cord, however,

not at a statistically significant level (Luglie et al., 2005; Daniels et al., 2007). No adverse

outcomes during the pregnancy (hypertension, premature rupture of membranes, caesarean

section rate, postpartum hemorrhage) or to the newborns (Apgar scores, preterm birth,

21

hypocalcemia, hypoglycemia, sepsis, respiratory distress, asphyxia, seizures) have been

ascertained (Hujoel et al., 2005; Luglie et al., 2005; Daniels et al., 2007). However, there was a

significant association between Hg levels in the cord blood and the number of amalgam

restorations in the mother (Palkovicova, Ursinyova, Masanova, Yu, & Hertz-Picciotto, 2008).

Although there were no significant associations between Hg and adverse outcomes in pregnancy

and newborns, the authors recommend that amalgam restorations in girls and women of

reproductive age should be used with caution, thus preventing prenatal Hg exposure.

Although there are multiple claims that amalgam is deleterious due to its mercury content, there

are no scientifically reputable studies that show any adverse health effects. This may be because

of the low amount of mercury released from amalgam or the steps taken to minimize mercury

toxicity such as the use of a rubber dam, as discussed below.

2.3.6.2 Allergy and Hypersensitivity

Only 50 cases in the past 100 years have been reported of a true allergy to amalgam (Eley, 1997;

Fuks, 2005). Among the <2% of patients who react to amalgam during patch testing, 37% of

them had a true allergy to mercury (Bains, Loomba, Loomba, & Bains, 2008). Some individuals

who have a pre-existing hypersensitivity or allergy to mercury may develop adverse reactions

such as an oral lichenoid reaction (Laeijendecker et al., 2004; Pezelj-Ribaric et al., 2008).

Amalgam allergy commonly presents as a delayed Type IV sensitivity (Forte, Petrucci, & Bocca,

2008). These symptoms often do not require treatment as they disappear within days of exposure.

However, in cases where there was a positive patch test reaction to mercury, the partial or

complete replacement of the amalgam resulted in a significant improvement (Laeijendecker et

al., 2004; Forte et al., 2008; Kal, Evcin, Dundar, Tezel, & Unal, 2008; McParland &

Warnakulasuriya, 2012). In a case report, a patient developed burning mouth syndrome

associated with a new amalgam tattoo after extraction of a tooth with an amalgam restoration

(Donetti, Bedoni, Guzzi, Pigatto, & Sforza, 2008). This patient reported an allergy to nickel.

Multiple case reports have shown orofacial granulomatosis related to amalgam restorations; after

removal of the restoration, symptoms disappeared within three months (Tomka et al., 2011;

22

Ellison, Green, Gibson, & Ghaffar, 2013). Overall, the incidence of mercury related allergies are

low and thus, amalgam should not be considered to have a high allergenic profile.

2.3.6.3 Minimizing Amalgam Toxicity

During clinical work with dental amalgam, the dental staff and patients may be exposed to both

metallic mercury and mercury vapour (Pohl & Bergman, 1995; Fuks, 2002). Dental personnel

have been found to have higher mercury in the urine than the general population; however, these

studies had poor mercury hygiene (Fuks, 2002). In general, when a rubber dam is used, the

plasma and urinary mercury levels can be considerably reduced (DeRouen et al., 2006). The

encapsulation of amalgam has reduced the amount of mercury exposure (Tezel, Ertas, Erakin, &

Kayali, 2001). Pohl and Bergman (1995) studied the influence of various excavating techniques

during the cutting, filling, and polishing of amalgam restorations and found that high volume

evacuation at a rate of 150L/min is the most effective (Pohl & Bergman, 1995). This allows the

mercury vapour levels to be in the range of 1-2 µg Hg/m3 in the breathing zone of the dentist

(Pohl & Bergman, 1995; Fuks, 2002). It is recommended that high volume suction and the use of

a rubber dam will help decrease mercury exposure to the patient and the dental team (Figure 2.4).

Figure 2.4- Mercury vapour levels from different measurement series: cut= cutting; fil=

filling; pol= polishing; HVE= high volume evacuator; ME= mirror-evacuator; SE= saliva

extractor (Pohl & Bergman, 1995).

23

In addition, to reduce the release of amalgam to the environment, chair side traps, amalgam

separator, vacuum pump filter, and line cleaners should be employed in every office (ADA,

October 2007) The American Dental Association, Canadian Dental Association, and

Environment Canada has developed guidelines to minimize potential health or environmental

issues for amalgam accumulation within dental office plumbing (Canada, 2002; Canada, 2004;

ADA, 2005).

2.4 Tooth Coloured Restorations

The materials included in tooth coloured restoration continuum extends from composite resin to

polyacid modified resin composites (compomers) to resin modified glass ionomers (RMGI) to

glass ionomer cements (GIC) (Berg, 1998).

2.5 Composite Resin

Composite resin is “a material system composed of a mixture or combination of two or more

micro or macro constituents which differ in form and chemical composition and are essentially

insoluble in each other” (Smith, 1990; Ruse, 1999). Methacrylate or dimethacrylate monomers

polymerize to form the matrix, which is filled to differing levels with glass and/or quartz (Berg,

1998). To ensure the chemical bonding of the filler and matrix, the filler particles are coated with

silane-coupling agents (Ruse, 1999). In order to create a cross-linked polymer, the polymerizable

monomers use visible light in a catalyzation reaction (Cramer, Stansbury, & Bowman, 2011).

Currently, composite resins are used in dental restorations, cements, crown and bridge facings,

and temporary crowns.

2.5.1 History

In 1958, composite resin was introduced as an alternative to the non-reinforced poly-methyl-

methacrylate used for restoration of the anterior teeth (Bowen, 1963, 1965; Kovarik, 2009). The

24

first composite resin was solely chemically cured using a base and catalyst reaction (Bowen,

1963). These restorations had many disadvantages such as poor colour stability, significant

polymerization shrinkage, low stiffness and hardness, and minimal binding to tooth structure.

Filler particles are now silane treated which; enhances the resin matrix bond, decreases the

polymerization shrinkage, lowers the coefficient of thermal expansion, and increases the

compressive strength and stiffness (Bowen, 1963; Kugel & Ferrari, 2000). In the 1970s, light-

cured composite resins were introduced, which allowed for longer working times and better

physical properties (Talib, 1993). At that time, microfill resins with a submicron particle size

were also introduced. The particle size created better wear characteristics and greater

polishability, enabling them to be used for both anterior and posterior restorations (Talib, 1993;

Jackson & Morgan, 2000).

Bonding allows for the creation of a more esthetic and longer lasting dental restoration by

sealing the dentinal tubules, thereby decreasing the potential for microleakage and recurrent

decay. However, the early attempts to bond to dentin resulted in poor bond strengths (Kugel &

Ferrari, 2000). This was believed to be due to the smear layer which is organic debris that

remains after the preparation of the dentin causing tubule blockage and making them

inaccessible for microtag formation. In 1955, Buonocore implemented the acid treatment of

enamel surfaces to enhance adhesion (Kugel & Ferrari, 2000). Acid etching allows the

hydroxyapatite on the surface of the enamel to dissolve, thereby opening the enamel prism

structure as well as removing the smear layer (van Noort, Gjerdet, Schedle, Bjorkman, &

Berglund, 2004). Bonding resin flows into the porosities in the enamel to form microtags,

allowing for the micro-mechanical retention of composites and decreased microleakage (Kugel

& Ferrari, 2000). Currently, there are numerous generations of bonding systems. It is suggested

that the “mechanical properties of the bonding mechanism achieved with hybrid layer and resin

tag formation can be greater than the forces of polymerization contraction” (Kugel & Ferrari,

2000). However, there is still a significant amount of polymerization shrinkage with modern

composites. This affects the longevity of composite and makes it inferior to amalgam, which is

self-sealing.

There have been many attempts to improve the antimicrobial and caries inhibiting properties of

composite resin. Fluoride salts such as sodium fluoride, potassium fluoride, and stannous

25

fluoride were added to the matrix; however, the effect of this was short-lived and it adversely

affected the mechanical properties (Swartz et al., 1976). Fluoroaluminiumsilicate-glass or

tetrabutylamonium fluoride incorporation into the monomer matrix, allow for an improved

release and storage of fluoride in in-vitro tests (Xu, Ling, Wang, & Burgess, 2006).

Chlorhexidine and silver ions have been shown to have a positive antimicrobial effect (Yoshida,

Tanagawa, & Atsuta, 1999). However, chlorhexidine adversely affects the mechanical properties

and silver changes the colour of the restorative material, so both have not been favourable.

Overall, composite, with its lack of antimicrobial activity, is at a disadvantage when compared to

amalgam since silver and mercury are both antibacterial (Roberts et al., 2008; Sousa et al., 2009;

Zimmerli, Strub, Jeger, Stadler, & Lussi, 2010).

2.5.2 Composition

The main composition of composite resin includes

Fillers made of quartz, silica, or glass;

Polymeric resin matrix;

Silane coupling agents; and

Other components such as pigments, stabilizers, polymerization inhibitor, photoinitiator,

and radiopaquing agents (Jackson & Morgan, 2000; Zimmerli et al., 2010; Cramer et al.,

2011).

Fillers, defined by weight and volume, are a major constituent of composite resin materials

(Dogon, 1990). The filler particles influence the properties of the composite such as;

polymerization shrinkage, the coefficient of thermal expansion, compressive strength, wear,

water absorption, and translucency (Jackson & Morgan, 2000; Kim, Ong, & Okuno, 2002;

Zimmerli et al., 2010; Delaviz, Finer, & Santerre, 2014). Historically, quartz has been used most

often; however, it has been more recently replaced with colloidal silica, silica with barium, or

lithium aluminum silicate (Soderholm, 1985). By increasing filler content, the compressive and

tensile strengths, modulus of elasticity, and wear resistance are generally increased (Kim et al.,

2002; Zimmerli et al., 2010). With round fillers, there is a higher filler content, allowing

26

increased hardness and flexural strength, while mixed fillers have no linear relationship (Kim et

al., 2002). In addition, the filler induced translucency can be varied with the heterogeneity in the

polymer matrix (Howard, 2010; Cramer et al., 2011). The mechanical properties of composite

have drastically improved with the creation of hybrid and nanofilled composites, thus starting to

overcome some of its inadequacies.

The resin matrix consists mostly of Bis-GMA (bisphenol-A-glycidylmethacrylate) (Zimmerli et

al., 2010). In comparison to methyl-methacrylate, Bis-GMA undergoes less polymerization

shrinkage, hardens more rapidly, and has superior mechanical properties (Delaviz et al., 2014).

However, when used by itself, its viscosity prevents the addition of high amounts of filler, thus it

is mixed in combination with short chain monomers such as TEGDMA for ease of handling

(triethylenglycol-dimethacrylate) (Zimmerli et al., 2010; Delaviz et al., 2014). This replacement

increases its tensile strength but can reduce the flexural strength of the material. The

dimethacrylate resin matrix has hydrophobic properties which make the placement of composite

resin technique sensitive. This makes composite resin more difficult to place in children who

have copious amounts of saliva and may need advanced behavior management.

2.5.3 Classification

Composite restorative materials are classified according to filler particle size, which ranges from

traditional to nanofilled (Mitra, Wu, & Holmes, 2003). The properties of the composite can be

changed according to the filler; with a smaller filler size, the composite has increased tensile

strength but the compressive strength is sacrificed.

Nanocomposites and hybrids have many advantages such as reduced polymerization shrinkage,

increased mechanical properties, and improved optical characteristics (Mitra et al., 2003;

Moszner, 2004). In addition, the wear resistance has been comparable or superior to that of

microfill and microhybrid composite resins (Yap, Tan, & Chung, 2004; Manuja, Pandit,

Srivastava, Gugnani, & Nagpal, 2011). Due to the improved properties, nanocomposites are

being used more often for both anterior and posterior restorations in primary and permanent

teeth.

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Table 2.1- Classification of Composite Resin

Category Particle Size (µm)

w/w% filler

Filler type Clinical Characteristics

Traditional 8-12 >80 Quartz Rough surfaces

Small Particle 1-5 60-78 Quartz and glass Better under large stresses

Microfilled 0.04-0.4 50-60 Colloidal silica, pre-polymerized composite

Good polishability Poor stress resistance, good esthetics, and radiopacity High amount of polymerization shrinkage

Hybrid 0.04, 1-5 50-75 Colloidal silica and glass

Good radio-opacity, polishability, physical properties, durability, esthetics comparable to microfilled High amounts of polymerization shrinkage

Nanofilled 5-25 75-100 clusters

75-80 Nanosilica, zirconium/ silica

Highly esthetic

Table is adapted from Donly’s AAPD Comprehensive Review Course Notes 2013, Lutz and

Philips 1983

2.5.4 Polymerization Process

There are two mechanisms for polymerization of composite resins: chemical or light-activated

cure. Polymerization occurs in three steps: initiation, propagation, and termination (Cramer et al.,

2011). Light activated composites contain a photoinitiator that is sensitive to blue light

(wavelength 470nm) and uses camphorquinone (CQ) as a photoinitiator. PPD (1-phenyl-1, 2-

propanedione) is a non-yellow photosensitizer that has been proposed as an alternative to

camphorquinone; however, it is currently not as efficient for visible light initiation (Cramer et

al., 2011). Since polymerization with pure Bisphenol-A(BPA) can be inhibited by moisture, the

liquid monomers in composite are commonly BPA derivatives such as BPA glycidyl-

dimethacrylate (Bis-GMA) and BPA dimethacrylate (Bis-DMA) (Fleisch, Sheffield, Chinn,

Edelstein, & Landrigan, 2010). When camphorquinone absorbs a photon, a short lived excited

state creates a complex with an amine, thus releasing free radicals (Cramer et al., 2011). The

radical created from photon absorption initiates polymerization with dimethacrylates such as

bisphenol-A-dimethacrylate (Bis-DMA), BisGMA, and triethlylene glycol dimethacrylate

28

(TEGDMA) as well as monomethacrylates such as tetrahydrofurfuryl methacrylate and isobornyl

methacrylate (Monroe & Weiner, 1969; Ruyter & Oysaed, 1982; Cramer et al., 2011).

The propagation and termination reactions are diffusion controlled; as the radical concentration

increases, polymerization rate also increases in a process called “auto-acceleration” (Cramer et

al., 2011). The polymerization rate is important as rapid curing is necessary for dental

composites. Termination involves a process called “vitrification” where the polymerization

reaction slows down and stops (Cramer et al., 2011). When this process stops there still may be

residual, unreacted methacrylates in the composite restoration (Cramer et al., 2011).

There are many factors which influence the amount of conversion of the monomers. The degree

of conversion of BisGMA monomer is approximately 55% for a chemically cured system and

48% for a UV cured system (Cowperthwaite, Foliy, & Malloy, 1981). Infrared spectroscopy

analysis of cured composite show 15-60% of methacrylate groups remains unreacted (Asmussen,

1982; Ruyter, 1985; Peutzfeldt, 1994; Park & Lee, 1996). Exposure to oxygen causes decreased

polymerization, leaving monomer in a liquid state on the outer surface of the material (Fleisch et

al., 2010). As the light is attenuated through the material, less light is able to activate the

polymerization deep within the material (Sustercic, Cevc, Funuk , & Pintar, 1993). Therefore,

increasing the distance between the light source and surface decreases polymerization (Park &

Lee, 1996). The rate of conversion is proportional to the degree of energy absorbed that can be

increased by using longer light polymerization time, increased light intensity, and pulsed laser

source (Nomoto, Uchida, & Hirasawa, 1994; Peutzfeldt, 1994; Sideridou & Achilias, 2005).

However, increased energy absorbance also causes an increase in pulpal temperature, potentially

causing an irreversible pulpitis (Daronch, Rueggeberg, Hall, & De Goes, 2007).

In addition, the composition of the monomer also affects the conversion. If there is greater water

uptake, the polymeric matrix can undergo swelling, allowing unreacted monomers and

degradation by-products to diffuse out of the resin creating gaps (Delaviz et al., 2014).

Furthermore, the ability of BisGMA to encounter free radicals is limited due to its large size and

relative lack of mobility (Chung & Greener, 1990; Delaviz et al., 2014). With a larger quantity of

BisGMA, there is a lower degree of conversion (Sandner, Baudach, Davy, Braden, & Clarke,

29

1997). TEGDMA, which is a less viscous monomer, allows for an increase in the number of

crosslinks, thus a greater amount of polymerization (Asmussen, 1982; Ruyter, 1985).

There are many enzymes in the oral cavity such as carbohydrate esterases, transferring enzymes

such as catalases and oxidases, proteolytic enzymes such as proteinase, and others such as

carbonic anhydrase (Delaviz et al., 2014). Of these enzymes, esterases actively degrade

composite resin. This hydrolytic degradation and subsequent water uptake allows the material to

be more prone to wear (Delaviz et al., 2014). The ongoing cycle of surface degradation and

material loss causes both salivary enzymes and micro-organisms to infiltrate between the tooth

and restoration margin. In comparison to ceramics and metals, these micro-organisms have a

higher affinity for composite which is speculated to be due to the higher affinity of salivary

proteins to polymeric materials. Unreacted leached monomer and surface roughness play a role

in the accumulation of plaque on the surface of the composite; however, it is unclear if it causes

enhanced bacterial adhesion. S. mutans, an etiological agent for dental caries, has esterase

activity which may also contribute to the degradation of composite resin. In addition, the hybrid

layer for the adhesive in composite is susceptible to degradation by matrix metalloproteinases

(MMP) which are present in human saliva (Delaviz et al., 2014). One theory is that the MMPs

that are normally bound to mineralized collagen fibrils may be activated in acidic conditions

such as with acid etching or through bacterial acid production, thus compromising the resin-

dentin interface (Delaviz et al., 2014). In addition, the bonds in the composite resin are also

subject to chemical hydrolysis by acids, bases, or enzymes, thus decreasing its strength.

Microleakage can cause secondary caries, adhesive failure, pulp inflammation, and post-

operative sensitivity (Braga, Ballester, & Ferracane, 2005; Cramer et al., 2011; Delaviz et al.,

2014). Polymerization shrinkage, which ranges from 2.5-6%, is a complex interaction between

the resin viscosity, volume shrinkage, polymerization rate, and degree of conversion (Shenoy,

2008). Volumetric contraction results in tooth distortion creating a gap between the tooth and the

restoration. A cavosurface interface gap will lead to microleakage of salivary fluids, enzymes

and micro-organisms into the margins (Braga et al., 2005; Shenoy, 2008).

To decrease the amount of microleakage, incremental and layered filling is needed to overcome

contraction stress (Braga et al., 2005). The use of an intermediate low-modulus layer over the

30

dentin, such as glass ionomer or resin modified glass ionomer may also help (Braga et al., 2005;

Cramer et al., 2011). If microleakage occurs, the strength of the composite resin dramatically

decreases. Research is currently being conducted to increase the bio-stability of composite resin

by altering the chemical structure of the monomer to make it bulkier and have a higher molecular

weight (Cramer et al., 2011).

2.5.5 Properties and Longevity

The main advantages of composite resin are excellent esthetics, preservation of tooth structure by

a minimally invasive preparation, and good compressive, flexural, and tensile strengths in

comparison to other tooth coloured restorations (Zimmerli et al., 2010). It can be a reliable

restorative material if used correctly, such as in a dry operating field with incremental filling and

sufficient polymerization; however, in the pediatric population, this may not be realistically

achieved.

Recently, more studies that favour the longevity and success rate of composite resin restorations

are being published. However, the practical application of those studies is limited (Shenoy,

2008). Unlike amalgam, it is difficult to find multiple studies with a long follow up time and

appropriate sample size with the same material (Shenoy, 2008).

Many studies evaluate composite resin with a two year follow-up, which show success rates as

high as 93.3%; with the goal that a restoration in a primary tooth should last until exfoliation,

one would have to speculate about future prognosis beyond two years (Papathanasiou et al.,

1994; Collins, Bryant, & Hodge, 1998; Hickel et al., 2005; Gjorgievska, Nicholson, Iljovska, &

Slipper, 2008; Gjorgievska, 2011). Among these studies, the main difference in outcomes was an

increased amount of wear in the composite restorations. A study by Wilder and colleagues in

1999 assessed the wear characteristics of composite at 17 years with a 65% follow-up (Wilder,

May, Bayne, Taylor, & Leinfelder, 1999). The mean pooled occlusal wear of four different light

cured posterior composites in the permanent dentition was 264 µm with 75% of the wear

occurring within the first five years. This study had a high success rate of 76% at 17 years with

31

the categories of failure being severe wear, secondary caries, fracture, post-operative sensitivity,

and operator error (Wilder et al., 1999).

One study evaluated the clinical and radiographic findings of Vitremer (light cured glass

ionomer), Z100 (composite resin), and amalgam with a two year follow-up (Fuks et al., 2000). It

was found that the prevalence of radiolucent defects at the cervical margin of a Z100 composite

(47%) was significantly higher than both amalgam (11%) and Vitremer (13%) (Figure 2.5).

Based on these results, it was suggested that composite resin should only be used for a primary

tooth if the expected lifespan is two years or less (Fuks et al., 2000).

Figure 2.5- The restoration on the primary left first maxillary molar shows a radiolucent

area under the composite resin. The arrow denotes a bubble (lack of material) on the distal

surface (Fuks et al., 2000).

Figure 2.6- The primary left first molar has a disto-occlusal composite that appears to have

good margins on the occlusal surface. After the tooth exfoliated, it exposed marginal

staining and surface defects on the proximal surface. (Fuks et al., 2000).

32

The New England Children’s Amalgam trial showed that composite restorations required seven

times as many repairs as amalgam restorations (DeRouen et al., 2006; Soncini et al., 2007).

Composite resin had a higher risk of secondary caries (3.5x) but the risk of fracture was 0.9

times lower than amalgam (Bernardo et al., 2007). In addition, single surface/small composite

restorations had a survival rate of 93.6% while restorations with four or more surfaces had a

survival rate of 50% after seven years (Bernardo et al., 2007). Five years after initial treatment,

the need for additional restorative treatment was approximately 50% higher in the composite

cohort (DeRouen et al., 2006).

In a practice-based retrospective study, composite resin and amalgam were compared for

survival over 12 years using low and high risk adult patient populations (Opdam, Bronkhorst,

Loomans, & Huysmans, 2010). In both populations at the five year follow-up, composite and

amalgam performed comparably. However, up to 12 years in the low-risk population, composite

showed a higher survival rate than amalgam with the adjusted failure rate being 1.68% and

2.41% (p=0.013), respectively (Opdam et al., 2010). It also had a better survival up to 12 years

for three and four/five surface restorations (p=0.02). However, in the high risk group, the 12-

year survival for three surface amalgam restorations was better than composite (p=0.03).

Although it appears that this study has a long follow-up time, it is misleading as it is not clearly

stated how many restorations were evaluated at the 12 year mark. In the inclusion criteria, the

follow-up had to be a minimum of 5 years but there is no information between 5 to 12 years;

thus, it appears that only estimates for longevity was reported. In addition, the authors state that

this study cannot be generalized as the results were from only one practitioner and the majority

of the amalgam restorations were placed earlier (1983-1993) than the composite resins (1996-

2003).

Although the properties of composite are improving, the longevity and wear characteristics are

still inferior to amalgam and stainless steel crowns. Composite may perform more favourably in

a low-risk population and when the conditions are ideal.

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2.5.6 Toxicity

Similar to amalgam, composite resin also has toxicity concerns as it contains BPA derivatives.

BPA is a synthetic chemical resin that is commonly used in; the production of plastic products

such as water bottles, polycarbonate plastic food storage containers, and epoxy resin lacquer

linings of metal food cans (Environment Canada, 2008; Fleisch et al., 2010). It is also used in;

automotive production, transportation equipment, DVDs, linings inside drinking water pipes,

carbonless paper coatings, and foundry castings (Agency, 2010). In 2007, more than 2.4 billion

pounds of BPA at an estimated value of almost $2 billion were produced in the US (Agency,

2010; Fleisch et al., 2010).

In Canada, the evidence relating to BPAs environmental persistence, bioaccumulation, and

toxicity has caused concern. Although BPA degrades fairly rapidly under aerobic conditions with

a half-life of a couple days, it is still widely detected in surface waters (Environment Canada,

2008). In addition, BPA is found in aquatic species, showing that BPA can be stored, which may

have potential bio-accumulation impacts.

There are three sources of BPA from dental materials: unpolymerized monomer on the surface of

the restoration, hydrolyzed polymers of bisphenol-derived monomers in the material, and finally,

fine particulate polymer produced by abrasion of the restoration (Santerre, 2007). Although pure

BPA is not a component of composite resin or dental sealants, it has been detected in saliva for

up to three hours after placement due to the hydrolysis of Bis-DMA by salivary esterases (Fung

et al., 2000; Sasaki et al., 2005; Fleisch et al., 2010).

According to the United States Environmental Protection Agency, a general agreement is that

BPA is a “reproductive and developmental toxicant at doses in animal studies of > 235 mg/kg-

bw/day (reduced fetal or birth weight or growth early in life, effects on testis of male rats) and >

500 mg/kg-bw/day (possible decreased fertility in mice, altered estrous cycling in female rats and

reduced survival of fetuses)” (Agency, 2010). BPA and Bis-DMA have been shown to be;

estrogen antagonists, androgen antagonists, and inhibitors of aromatase activity at the receptor

level (Fleisch et al., 2010). In female rats exposed to BPA there has been; increased uterine

weight, premature vaginal opening, and increased proliferation of mammary epithelial cells.

Other animal studies noted; increased aggression, delayed onset of puberty, decreased number of

34

offspring, and decreased birth weight after a high concentration of prenatal exposure of BPA

(Fleisch et al., 2010). These studies commonly used Bis-DMA, not Bis-GMA, which is seen

more often in composite resin. However, when Bis-GMA is placed in direct contact with

fibroblasts, it causes significant toxicity in in-vitro studies (Wataha, Hanks, Strawn, & Fat,

1994).

Since these studies were conducted in animals, there is controversy about whether the effects are

relevant. It is speculated that rodents may be more sensitive to the effects of BPA. Rodents have

more free-BPA, which is more estrogenic than the metabolite BPA-glucuronide (Agency, 2010).

However, direct human epidemiologic studies have shown an association between BPA; and low

follicle stimulating hormone level in occupationally exposed women, polycystic ovary

syndrome, and high testosterone levels in both men and women (Fleisch et al., 2010). Bound and

free BPA concentrations in amniotic fluid were five times higher compared to serum and

follicular fluid; this could lead to an accumulation of fetal circulating levels and an elevated in

utero exposure (Wataha et al., 1994). There is an association between chromosomal defects with

prenatal exposure which may be due to the limited activity of the glucuronidation enzymes in the

human fetal liver (Ring, Ghabrial, Ching, Smallwood, & Morgan, 1999; Fleisch et al., 2010).

Several top-selling sealants and composites in the United States do not disclose the specific

monomer composition of their resins; those that do often use unique monomer structures that

have not been tested for estrogenicity or use generic descriptions (Fleisch et al., 2010). In 2007,

all sealants that carry the Seal of the American Dental Association (a product recognition

program that has been discontinued) released detectable amounts of BPA (Azarpazhooh & Main,

2008). In the US, the majority of the government BPA assessments have considered BPA levels

in dental composites insufficient for the purposes of policy amendment and hazard evaluation.

However, in Canada, it was acknowledged that there is a “high uncertainty in the data” and the

country took precautionary action by banning the use of BPA in baby bottles in June 2009

(Agency, 2010). Public perceptions of BPA toxicity may steer research developments towards

alternatives such as urethane dimethacyrlate and polyhedral oligomeric silsesquioxane

methacrylates (Cramer et al., 2011).

35

In the liver, first pass metabolism creates an inert BPA-monoglucuronide which has no endocrine

activity. It is rapidly excreted in urine with a half-life of less than 6 hours; therefore, it is

expected that very low concentrations of free BPA would be available for receptor binding in

humans (Volkel, Colnot, Csanady, Filser, & Dekant, 2002; Tominaga et al., 2006). However,

there are a few reports of adverse reactions in patients caused by resin-based materials (van

Noort et al., 2004; Tillberg, Stenberg, & Berglund, 2009). The most common adverse effects

were; contact dermatitis, intraoral ulcers, swollen lips, and respiratory reactions such as

pharyngeal edema and asthma (Kanerva et al., 2000; Tillberg et al., 2009). The majority of

symptoms were primarily intraoral and appeared within the first 24 hours after treatment. Within

less than a week, half of the reactions disappeared (Tillberg et al., 2009). Dental composites pose

a risk for local adverse reactions such as mucosal or skin reactions, but the quantity of the

composite is most likely too small for systemic changes (Tillberg et al., 2009).

In order to dramatically reduce the amount of unreacted monomer, immediate removal of the

unpolymerized superficial layer by gargling with water for 30 seconds after composite placement

has been shown to decrease BPA to baseline levels for 9 different resins (Fleisch et al., 2010).

Other studies have shown that pumice on a cotton ball or in a prophylaxis cup is more effective

than using dry cotton pellets or air/water spray to eliminate absorption of bis-DMA, bis-GMA,

and TEGDMA (Fleisch et al., 2010). In addition, the use of a rubber dam is helpful to decrease

potential absorption (Fleisch et al., 2010).

Another issue with composite resin is post-operative sensitivity. Dental hypersensitivity has been

related to the fluid flow within the dentinal tubules, most likely due to differences in osmotic

pressures (Brannstrom, 1967; Brannstrom, 1968; Baratieri & Ritter, 2001). Baratieri and Ritter

(2001) found that 24% of teeth restored had post-operative sensitivity. After four years, all teeth

were vital and did not exhibit sensitivity (Baratieri & Ritter, 2001). Thus, although composite

resin has been marketed as an esthetic material with lower toxicity than amalgam, it is not a

benign material and its toxicity must continue to be researched.

36

2.6 Glass Ionomer Restorations

Glass ionomer cement (GIC) is a fluoride releasing salt that is formed by a chemical reaction

between a polyalkenoic acid and an aluminum-containing glass (Wilson, 1988; Berg, 1998).

Glass ionomers can be used as a liner, luting cement, or a base/core material. It possesses the

unique properties of having a true chemical bond to tooth structure, minimal or no

polymerization shrinkage during setting, a coefficient of thermal expansion similar to tooth

structure, and anticariogenic action due to fluoride release (Berg, 1998; Paschoal et al., 2011).

2.6.1 History

Glass ionomer cement was invented in the 1960s; however only started to gain popularity about

twenty years later when the Atraumatic Restorative Technique (ART) was developed for non-

industrialized countries where there was limited access to dental care (Frencken, Pilot,

Songpaisan, & Phantumvanit, 1996; Ersin et al., 2006; Palotie, 2009). ART was originally

pioneered in Tanzania by the University of Dar es Salaam as a community based primary oral

health care program (Frencken et al., 1996; Mandari, Frencken, & van't Hof, 2003). It consists of

caries removal with hand instruments, thus no electricity was needed, combined with a

restorative material that can adhere to the tooth. Recently, this technique has been gaining wider

acceptance for the treatment of young, uncooperative children (Christensen, 2001; Ersin et al.,

2006). GIC utilization is highest in Iceland and Australia (17%) and lowest is in Brazil (1%)

(Tyas, 2005; Braga, Vasconcelos, Macedo, Martins, & Sobral, 2007).

Glass ionomers are unique restorations due to their chemical adhesion to tooth structure and

fluoride release. Unfortunately, the strength, durability, longevity of GIC’s is less than other

direct restorative materials (Welbury, Walls, Murray, & McCabe, 1991; Espelid, Tveit, Tornes,

& Alvheim, 1999; Hickel et al., 2005). There have been multiple attempts to improve their less

than ideal mechanical properties (Ruse, 1999). One approach included substituting the glass with

silver-tin-copper amalgam alloys, however, both in-vitro and in-vivo results were poor

(Simmons, 1983; Ruse, 1999). Another attempt was changing the properties of the acid-soluble

glass by incorporating silver to create a “cermet” filler (McLean, Powis, Prosser, & Wilson,

1985). These are still available on the market.

37

2.6.2 Characteristics

Glass ionomers set as the result of an alkenoic acid-base polymer reaction in an aqueous

environment (Ruse, 1999). The majority of the crosslinking of the polymeric chains are due to

ionic bonds; however, there are also a large number of secondary bonds which determine the

mechanical properties of the material. When the acid-base reaction occurs, calcium, aluminum,

sodium, fluoride, and silicate ions are released from the acid- soluble glass. This silicagel layer is

rich in fluoride and surrounds the unreacted glass particles. The process of water sorption and

desorption facilitates the ion exchange of fluoride and hydroxyl which allows the fluoride to be

released into the oral environment from a set glass ionomer (Ruse, 1999).

Glass ionomer provides the advantage of having a true chemical bond and similar coefficient of

thermal expansion as tooth structure, especially dentin (Berg, 1998; Ruse, 1999). However, the

material is brittle, has low modulus of elasticity, and low tensile strength (Crisp, Jennings, &

Wilson, 1978; Mitchell, 1997). The chemical bond can be disrupted if subjected to strong

opposing forces such as dysfunctional occlusion during excursive movements. Biologically,

GICs have been reported to cause some pulpal post-operative inflammatory responses that

resolve within a month of placement (Smith & Ruse, 1986).

Glass ionomers absorb water in the first 24 hours after placement; some authors believe that the

hygroscopic expansion may reduce marginal gaps (Toledano, Osorio, Osorio, & Garcia-Godoy,

1999). This theoretically, may allow glass ionomer and resin modified glass ionomer to have less

microleakage than resins, but in clinical studies this has not been demonstrated (Attin, Buchalla,

Kielbassa, & Helwig, 1995; Toledano et al., 1999).

2.6.3 Fluoride Release

An important component of glass ionomer is its fluoride content as it adds to the therapeutic

value of the restoration (Paschoal et al., 2011). Fluoride release from glass ionomers can occur

by three mechanisms: surface loss, diffusion through pores and cracks, and bulk diffusion

(Paschoal et al., 2011). When studying fluoride release, there can be a large variability in the

38

results secondary to extrinsic factors which include type of storage medium, experimental

design, and analytical methods. When the fluoride ions are released, they can be taken up by the

enamel and dentin, thus decreasing the susceptibility to acid challenge and disrupting the

bacterial metabolism which produce organic acids (Forsten, 1994; Donly & Nelson, 1997; Tam,

Chan, & Yim, 1997; Ewoldsen & Herwig, 1998). The fluoride release dissipates to 10% of its

original amount 3-4 weeks after placement but can continue to leach up to two years (Swartz,

Phillips, & Clark, 1984; Forsten, 1994; Berg, 1998; Dhondt, De Maeyer, & Verbeeck, 2001). In

an in-vitro study, Forsten (1990) found that fluoride release is increased with a lower pH, thereby

allowing an additional benefit in times of acidity. Fluoride in the glass ionomer can be

replenished from the oral environment through salivary fluoride from dentifrices, mouthwashes,

and professional fluoride application although it is rapidly released (Swartz et al., 1984; Forsten,

1994; Donly & Nelson, 1997). Many in-vitro studies have reported the antibacterial properties of

fluoride and the potential of remineralization effects but clinical studies have not been

conclusive; thus fluoride may not have a clinical advantage (Tyas, 1991; Ersin et al., 2006).

2.7 Resin-Modified Glass Ionomer

Resin-modified glass ionomer (RMGI) was created to overcome the perceived inadequacies of

traditional glass ionomers including; brittleness, low flexural strength, short working time, long

set time, dessication after setting, and poor esthetics (Paschoal et al., 2011). In addition to the

components of GIC such as fluoroaluminosilicate glass and a water soluble acid, RMGI is

strengthened by adding a hydrophilic resin material and photoinitiator (McLean, Nicholson, &

Wilson, 1994). The first RMGI was created by grafting unsaturated carbon-carbon chains onto

the polyalkenoate backbone of the glass ionomer using a mixture of composite resin monomers,

such as Bis-GMA and 2-hydroxyethyl methacrylate (HEMA), as a co-solvent (Ruse, 1999). The

unsaturated carbon-carbon bond enables covalent crosslinking within the matrix, thus improving

the mechanical properties (Ruse, 1999). The photoinitiator causes the glass to be silanized, which

allows the adherence of glass within the resin matrix (Berg, 1998).

39

2.7.1 Setting Process

RMGI sets by two main mechanisms: polymerization of the monomer by either visible light or

chemical cure and the acid-base glass ionomer reaction (Berg, 1998). Although the acid-base

reaction allows the material to be set without light, optimum properties are achieved with light

polymerization. Some RMGIs have a “tri-cure” mechanism which incorporates an acid-base

reaction, visible light curing of the methacrylate groups, and a chemically activated

polymerization of methacrylate groups (Cox, 1993). Therefore, if all areas are inaccessible to the

curing light, it can continue to set, thereby increasing its mechanical properties.

2.7.2 Characteristics

Similar to GIC, RMGI has chemical adhesion to enamel and dentin, biocompatibility, and

fluoride release (Cox, 1993; Momoi & McCabe, 1993; Forsten, 1994; Attin, Vataschki, &

Hellwig, 1996). However, it also exhibits improved physical properties such as increased tensile

strength (Wilson, Prosser, & Powis, 1983; Burgess, Barghi, Chan, & Hummert, 1993; Attin et

al., 1996). The main disadvantages of the material include the handling properties (proper

mixing), polymerization shrinkage, strength, and seal (Berg, 1998).

When assessing fluoride release, the extrinsic factors mentioned earlier, such as storage medium,

experimental design and analytical factors, make it difficult to compare data between studies. In

comparison to GIC, some studies have found that RMGI has less, similar, or more fluoride

release (Momoi & McCabe, 1993; Robertello, Coffey, Lynde, & King, 1999; Vermeersch,

Leloup, & Vreven, 2001). An in-vitro study of nanofilled resin composite (Filtek Supreme-RC),

conventional GIC (Ketac Molar- KM), nanofilled RMGI (Ketac N100-KN), and RMGI

(Vitremer- V) evaluated the fluoride release for 15 days (Paschoal et al., 2011). The nanofilled

RMGI and RMGI both had a strong relationship between cumulative fluoride release and time

(Figure 2.7a). In terms of daily fluoride release, the amount released from each material was

similar (Figure 2.7b).

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Figure 2.7a/b- The above figures exemplify how Vitremer, a resin-modified glass ionomer,

has the most cumulative fluoride release. In terms of daily fluoride release, all of the glass

ionomers release similar amounts of fluoride.

2.8 Compomer (Polyacid Modified Composite Resin)

Compomers are polyacid modified composite resins which combine the properties of composite

and GIC (Ruse, 1999; Zimmerli et al., 2010). It allows for good esthetics similar to composite,

minimal steps in placement, easy handling with no mixing, and fluoride release (Berg, 1998).

The glass ionomer components are unable to promote enough acid-base reactions for a full

chemical cure so it must have visible light activation for polymerization (Berg, 1998).

2.8.1 History

In the 1990s, the original aim of the manufacturers was to produce a material that bonded to

tooth substance without the need for acid etching (Hickel & Voss, 1990; Welbury, Shaw,

Murray, Gordon, & McCabe, 2000). The main reason was to overcome the technique sensitive

mixing and handling of the RMGI. One of the goals of compomers was to avoid acid etching,

however, leakage is reduced when the enamel margins are etched prior to the restoration

placement (McLean et al., 1994; Berg, 1998).

41

2.8.2 Characteristics

Compomers have two main constituents: dimethacrylate monomers with two carboxylic groups

and filler similar to the silanized ion leachable glass present in GIC (Ruse, 1999; Zimmerli et al.,

2010). In comparison to RMGI which has polyalkenoic acid polymers, compomers contain acid-

decomposable glass and acidic, polymerizable monomers (Welbury et al., 2000). The particle

size of the fillers can range from 0.2µm to 10µm, thus allowing for good finishability and

esthetics (Zantner, Kielbassa, Martus, & Kunzelmann, 2004). Unlike GIC and RMGI, the

dominant setting reaction is the photopolymerization of resin (Welbury et al., 2000). In order to

achieve sufficient retention, the dental hard tissue must be pre-treated with an adhesive system

similar to composite (Gjorgievska et al., 2008; Zimmerli et al., 2010).

An advantage is the combination of fluoride release of glass ionomers, albeit to a lower degree,

and the physical properties of composite resin (Welbury et al., 2000). The polymer components

absorb minimal water, which permits a long term acid-based reaction that allows for fluoride

release (Welbury et al., 2000). In-vitro, the initial fluoride release was 28 days and had an

inhibitory effect on caries development in the adjacent tooth (Lennon, Wiegand, Buchalla, &

Attin, 2007; Zimmerli et al., 2010). However, in regard to the release rates, it is more similar to

fluoridated composite resins than GIC (Aboush & Torabzadeh, 1998). In comparison to

composite resin, the surface hardness, compressive strength, and flexural strength are

approximately 50%, 70%, and 80%, respectively (Meyer, Cattani-Lorente, & Dupuis, 1998;

Ruse, 1999). Compomer initially contracts with polymerization but also expands up to 3% due

to water uptake after placement (Hallett & Garcia-Godoy, 1993). Polymerization shrinkage of

any resin-containing restoration can lead to marginal discrepancies, causing recurrent decay,

marginal discolouration, microleakage, and sensitivity (Toledano et al., 1999). Biologically,

there is little evidence of adverse pulpal reactions when bonding systems are employed and

leakage is reduced when the enamel margins are etched. The bond strength measurements are not

as high as with dentin bonding systems (Wilson et al., 1983; Attin et al., 1996).

42

2.8.3 Longevity for Tooth Coloured Restorations

The success rates for GIC, RMGI, and compomer vary greatly depending on the setting where

the restorations were placed; academic or private practice, brand of the material, and follow-up

time. Hickel et al. (2005) meta-analysis of the longevity of posterior restorations in the primary

dentition shows the variability of the data in the literature. Table 2.2 below demonstrates that

with increasing study duration, a decrease in success rate occurs although most of the studies

included in the analysis involved very small sample sizes with short term follow up.

Table 2.2- Success rates (%) of Primary Molar Restorations by Observation Period

Study Duration (yrs) 2 3 4 5 6 7 8 9

Stainless steel crown (SSC)

Mean 86.6 58 86.7 85 88

Min 75 58 68 83 88

Max 97 58 100 83 88

Number of readings 7 1 3 1 1 Amalgam Mean 80.5 67.8 61 72.2

Min 29.4 14 55 36

Max 100 96.5 67 95.9

Number of readings 12 12 2 7 Glass ionomer Mean 80.1 66.8 67.4 79

Min 66 16.3 9.5 67

Max 98 100 93.3 91

Number of readings 5 15 4 2 ART Restorations Mean 75.5 66.2

Min 41.7 54

Max 96 86.1

Number of readings 6 4 Composite Mean 89.8 85.1 85.8 88 38

Min 71 40 75.9 88 38

Max 100 100 95.6 88 38

Number of readings 8 7 2 1 1 Compomer Mean 93.3 87.6 91 91

Min 78 79.5 91 91

Max 100 94.1 91 91

Number of readings 7 3 1 1

For GIC, the annual failure rates for Class I restorations can range between 0% to 17% while for

Class II restorations, range from 0.8% to 25.8% (Welbury et al., 1991; Papathanasiou et al.,

1994; Espelid et al., 1999; Welbury et al., 2000; Rutar, McAllan, & Tyas, 2002; Hickel et al.,

2005). In two-year studies, the success rate of conventional GIC Class I restorations have been

reported as high as 75% (Qvist, Laurberg, Poulsen, & Teglers, 1997; Hickel et al., 2005). One of

the main reasons for the great variability in failure rates may be the variety in placement

43

techniques used in these studies. The main reasons for failure were secondary caries, fracture,

and lost restorations (Hickel et al., 2005). The study with the lowest failure rates, Class I (0%)

and II (6.6%) restorations, had a follow-up of three years. This low failure rate may be due to

specific case selection and a higher compressive strength achieved by mixing a high powder to

liquid ratio (Rutar et al., 2002). Teeth were chosen only if the caries did not involve the isthmus

which is atypical of cases encountered in private practice (Rutar et al., 2002).

RMGI has an approximately 50% reduced risk of fracturing when compared to a conventional

GIC (Mjor et al., 2002; Hickel et al., 2005). Class V RMGI restorations were reported to have

significantly less microleakage compared to composite resins (Attin et al., 1995; Toledano et al.,

1999) most likely due to the lack of enamel available for bonding at the gingival seat.

The distribution of failure rates for Dyract, the first compomer available, ranged from 4% to 22%

over two years (Kavvadia, Kakaboura, Vanderas, & Papagiannoulis, 2004). In a two-year study

comparing amalgam and a more recent compomer, F2000 (3M), for Class II restorations, there

were significant differences in the marginal adaptation and anatomical form. No significant

difference was found between the failure of the restorations and development of secondary caries

(Kavvadia et al., 2004). Other two-year follow-up studies have shown compomers placed with

rubber dam isolation and acid etching have a success rate of 93-100% (Mass, Gordon, & Fuks,

1999; Gjorgievska, 2011). Although these studies show a good success rate, two years is not

enough time to adequately evaluate the material regarding longevity.

Hse and Wei (1997) used 50 matched bilateral pairs of primary teeth to compare the clinical

performance of a compomer (Dyract) with a hybrid composite resin (Prisma TPH) (Hse & Wei,

1997). The overall failure rate for Dyract was 1.7% due to secondary caries, colour instability,

poor marginal integrity, or poor anatomic form. With a very short follow-up of only one year and

a relatively small sample size, the authors concluded that compomer is a suitable alternative to

amalgam. Other studies have reported the success rate for Class II restorations over three years to

be 79.5% (Attin et al., 1996; Hickel et al., 2005). In cervical restorations, compomer performs

better than resin-modified glass ionomers but not as well as composites (Folwaczny, Loher,

Mehl, Kunzelmann, & Hinkel, 2000; Folwaczny, Loher, Mehl, Kunzelmann, & Hickel, 2001;

Gjorgievska et al., 2008).

44

The New England Children’s Amalgam trial had a follow-up of 5 years with 954 amalgam

restorations and 1088 compomer or composite restorations in primary teeth (Soncini et al.,

2007). According to this trial, the difference between longevity of compomer and amalgam was

not significant; however, compomer was replaced significantly more frequently than amalgam

(5.8 % vs. 4%, respectively) due to recurrent caries. Thus, the results are misleading and it could

be misinterpreted that compomer is equivalent to amalgam.

In 2000, Welbury created a cumulative survival curve for five materials; glass ionomer cement

(Ketac fil), fast setting glass ionomer cement (Chemfil superior), amalgam, a glass cermet (Ketac

silver), and compomer (Dyract) incorporating studies published in 1991, 1995, and 2000

(Welbury et al., 1991; Kilpatrick, Murray, & McCabe, 1995; Welbury et al., 2000; Kilpatrick &

Neumann, 2007). Evaluation of the results should take into account that although the

methodologies are identical, the conditions in which the restorations were placed may have been

different (Welbury et al., 2000). Dyract had the highest cumulative proportion surviving for this

study and was superior in terms of; anatomic form, marginal integrity, cavosurface discoloration,

recurrent caries, maintenance of interproximal contact, surface texture, and overall failure

(Figure 2.8). However, out of the 56 original pairs 36 pairs were excluded for the following

reasons; 15 pairs failed due to exfoliation prior to censor date, 14 pairs due to failure of one/both

restoration prior to censor date, 1 pair failed due to caries elsewhere on the tooth, and 6 pairs

failed due to a loss to follow-up.

45

Figure 2.8- The combined survival curves from 1991, 1995, and 2000 for overall failure of

five restorative materials.

Overall, there is a large variability in the data showing the success rates of glass ionomer, resin-

modified glass ionomer, and compomer. Due to the small sample sizes and short term follow-up

in many of the studies, composite, amalgam, and stainless steel crowns are still superior

materials in terms of durability, marginal integrity, and longevity.

2.9 Stainless Steel Crown

Stainless steel crowns (SSCs) were introduced into the dental market in 1960 by Engel (Randall,

Vrijhoef, & Wilson, 2000; Zinelis, Lambrinaki, Kavvadia, & Papagiannoulis, 2008). It is a

prefabricated crown which must be adapted to each individual tooth and cemented with a

biocompatible luting agent (AAPD, 2012). The composition of the older alloys was 77% nickel,

15% chromium, and 7% iron. Currently, the alloys composition has changed to consist of 18%

chromium, 8% nickel, and a carbon content of 0.08-0.12% (Zinelis et al., 2008). The higher

chromium content reduces corrosion of the material (Zinelis et al., 2008).

SSCs are “extremely durable, relatively inexpensive, subject to minimal technique sensitivity

during placement, and offer the preventive advantage of full coronal coverage with esthetics

being the main disadvantage (Seale, 2002). SSCs are indicated for the “restoration of primary

and permanent teeth with caries, cervical decalcification and/or developmental defects when;

failure of other available restorative materials is likely, following pulpotomy or pulpectomy, for

restoring a primary tooth that is to be used as an abutment for a space maintainer, or for the

intermediate restoration of fractured teeth” (Randall et al., 2000; Seale, 2002; Mackert & Wahl,

2004; AAPD, 2012). For a Class II restoration, a flared proximal box can weaken the tooth and

reduce support for the restoration; therefore, SSC would be an appropriate choice of restorative

material (Braff, 1975; Randall et al., 2000). Unlike amalgam, which requires retention features to

be added into its preparation, the preformed crown is retained by the flexibility of its thin, pre-

contoured crown margins, allowing it to engage in the undercut area apical to the cemento-

enamel junction in a primary molar (Randall et al., 2000) and the cement. In addition, a strong

46

advantage of the SSCs is its minimal technique sensitivity; in an uncooperative, crying child. A

well-fit SSC can be placed without compromising the longevity or quality of the restoration

(Seale, 2002).

2.9.1 Stainless Steel Crown Concerns

SSCs can be precontoured and crimped or uncrimped, which requires the operator to fit the

crown for that individual tooth. The goal of the margins is to replicate the natural cervical

contours of enamel at the cement-enamel junction and aid in the retention (Croll, Epstein, &

Castaldi, 2003). Pre-crimped crowns resemble the normal tooth form with a curved axial design

and anatomically-defined occlusal surface. Most modern anatomically-contoured crowns should

need minimal modification (Randall et al., 2000). Uncrimped SSCs have flat axial surfaces

which require adaptation to replicate crown configuration; these are useful if the spatial

relationships in an arch require broader and flatter proximal contacts or if the tooth preparation

has a greater inciso-apical length. Both types of crowns require final adaptation of the margin by

the dentist to customize the marginal fit for each individual tooth preparation (Croll et al., 2003).

If the crown does not fit well, the preparation margin should be checked for adjustment (Randall

et al., 2000). Poorly adapted SSC margins can affect periodontal tissues and cause delayed

eruption of adjacent teeth (Croll et al., 2003; Sharaf & Farsi, 2004). When crowns are judged to

be radiographically inadequate due to poorly adapted margins and close approximation to bone,

interproximal bone loss may occur (Sharaf & Farsi, 2004).

2.9.2 Longevity

A 2007 Cochrane review about the efficacy of SSCs found no studies that met the inclusion

criteria (Innes, Ricketts, & Evans, 2007). This review calls for more prospective randomized

controlled trials but explicitly states that the absence of evidence should “not [be] misinterpreted

as evidence for their lack of efficacy” (Innes et al., 2007; Brickhouse, 2011). Randall’s 2000

meta-analysis showed that the failure rates ranged from 1.9-30.3% for stainless steel crowns and

11.6-88.7% for amalgam restorations (Randall et al., 2000). A pooled odds ratio from the studies

47

assessed in Randall’s 2000 meta-analysis yielded an OR =0.23 (95%CI =0.19-0.28) in favour of

SSC over amalgam (Randall et al., 2000; Brickhouse, 2011). Roberts and Sherriff (1990) carried

out a 10-year evaluation of 1688 amalgam restoration and 716 stainless steel crowns on primary

molar teeth (Roberts & Sherriff, 1990). For preformed crowns, the true failure rate was 1.9% and

the 5-year survival estimate was 92%, leading to an estimated median survival time of greater

than 7.64 years (Roberts & Sherriff, 1990). One study by Dawson et al (1981) reported that SSCs

showed a survival rate of 87.5% while the survival rate for one-surface amalgam was 63.2%, and

for two-surface amalgam restorations was 29.4% (Dawson, Simon, & Taylor, 1981).

In high caries-risk children, definitive treatment of primary teeth with SSCs may be more

successful over time than multi-surface restorations (Braff, 1975; Dawson et al., 1981; Holland

et al., 1986; Papathanasiou et al., 1994; Randall et al., 2000; AAPD, 2012). In addition, if there is

poor parent compliance and a possible lack of follow-up, some authors suggest using SSCs

(Fuks, 2002; Seale, 2002). Medicaid data from the United States support the concept that as a

nation, “the poor do not seek regular dental care and tend to seek care for pain relief” (Services,

2000). For children under the age of four, SSCs have a greater success rate than amalgam; the

success rate may be as high as two to sevenfold greater for each year up to 10 years of service

(Randall et al., 2000). With the increasing age of the child at initial placement, the percentage of

true failures of restorations decreased twofold (Hunter, 1985; Levering & Messer, 1988). For

children with early childhood caries, the marginal adaptation and anatomical form was better for

crowns placed in patients treated using general anesthesia versus conscious sedation (Roberts &

Sherriff, 1990). The main reasons for restoration failure are perforation of the crown or need for

recementation (Randall et al., 2000). Although more randomized controlled trials are needed,

SSCs have a favourable outcome for severely decayed, multi-surface, post-pulp treated primary

molars.

2.10 Rubber Dam Isolation

Rubber dam isolation has been utilized for over 100 years for moisture control and retraction of

soft tissue (Soldani & Foley, 2007; Gilbert et al., 2010). The benefits of rubber dam isolation

48

include improved access and visibility of an isolated operating field, reduction of environmental

contamination by salivary aerosol, protection from aspiration of foreign bodies such as debris

and dropped instruments, moisture control, reduction of nitrous oxide gas levels in the room air

from mouth breathing, and facilitation of treatment in patients with a pronounced gag reflex

(Figure 2.9) (Cochran, Miller, & Sheldrake, 1989; Christensen, 2001; Lynch & McConnell,

2007; Soldani & Foley, 2007; Slawinski & Wilson, 2010). Other suggested benefits are

dependent on the personalities of the dentist and patient for behaviour management (Christensen,

2001; Soldani & Foley, 2007). For example, a nervous and uncooperative child may settle once

the rubber dam is in place, which is speculated to be from the child dissociating from the

procedure (Jones & Reid, 1988). As a result, the dentist may also have reduced stress when

completing restorations. In addition, some suggest that rubber dams reduce procedure time due

to lack of expectoration and repositioning of the operating field after each expectoration

(Christensen, 2001; Slawinski & Wilson, 2010). The saliva accumulation behind the rubber dam

can be easily swallowed or suctioned (Jones & Reid, 1988; Christensen, 2001).

Figure 2.9- Relative importance of reasons for using rubber dam isolation (Soldani &

Foley, 2007).

During restorative treatment, the spread of salivary aerosol particles and splatter is a major

concern (Cochran et al., 1989). Many studies have confirmed that dental procedures generate

bacteria-laden aerosol particles that contaminate the air, face, and eyes of both the patient and the

dental team (Micik, Miller, Mazzarella, & Ryge, 1969; Szymanska, 2007). Micik et al. (1969)

49

quantified the amount of bacterial aerosols generated from dental procedures in comparison to

common naso-oral activities such as breathing, speaking, coughing, sneezing, and brushing teeth.

Prophylaxis with a pumice cup, pumice, and an air-turbine handpiece produced a similar amount

of bacteria as coughing. In addition, when an air-turbine handpiece is used with an air-water

spray, the amount of aerosol is similar to sneezing. Rubber dam usage and high speed suction has

been found to dramatically reduce the bacterial aerosol levels (Micik et al., 1969; Szymanska,

2007). Reducing the amount of saliva in the operating field with the rubber dam also results in a

reduction of the spread of potentially infectious agents (Cochran et al., 1989).

Rubber dam (RD) usage varies depending on the tooth location and restoration material. For the

success of composite restorations, many consider the use of rubber dam “an essential component

of modern adhesive dentistry” (Knight, Berry, Barghi, & Burns, 1993; Hill & Rubel, 2008).

Multiple studies have shown that rubber dam isolation may be used more often for composite

resin restorations than for other materials (Jones & Reid, 1988; Knight et al., 1993; Gilbert et al.,

2010). However, in 2008, a survey of US general dentists regarding rubber dam usage showed

that RD was never used; 39% for posterior composite resins, 45% for anterior composite resins,

and 53% for amalgam restorations (Hill & Rubel, 2008). In Ireland, general dentists would not

use rubber dam isolation for the majority of posterior composite resins 52%, anterior composite

resins 59%, and posterior amalgam restorations 77% (Lynch & McConnell, 2007). For the

placement and removal of amalgam restorations, the use of a rubber dam significantly decreases

the peak of mercury in the patient’s plasma (Berglund & Molin, 1991; Kremers et al., 1999).

Surveys of general dentists suggest that the use of a rubber dam is limited due to the perception

that it is time consuming, inconvenient, unnecessary, and difficult to place (Cochran et al., 1989;

Christensen, 2001; Soldani & Foley, 2007; Hill & Rubel, 2008). Other reported reasons to not

use the rubber dam include patient discomfort, cost, and low fees for treatment (Lynch &

McConnell, 2007). For patient acceptance, Gergely (1989) reported in a sample of 72 subjects,

98.6% accepted and 72.2% preferred treatment with the rubber dam. The main criticism

especially by children was associated with the initial placement of the rubber dam. In a survey

conducted in a children’s dental health unit in Scotland, 30% preferred the rubber dam while

49% stated that the rubber dam made no difference to treatment (Jones & Reid, 1988). Of the

21% of the sample who reported treatment without the rubber dam, 18% stated that it was

50

painful and/or uncomfortable. To address this complaint, topical or local anesthetic could be

administered. Overall, a high acceptance for the rubber dam was noted in children. In regards to

time, the average amount of time required for rubber dam placement in children, on average, was

found to be 106 seconds (Heise, 1971).

A prospective survey of paediatric dentists in the United Kingdom found that rubber dams were

used most often by 31-40 year old dentists and in private practice rather than in mixed or

governmental practices (Soldani & Foley, 2007). In regard to endodontic procedures, permanent

tooth endodontics were more likely to have rubber dam isolation than primary tooth endodontics

(χ2

=77.28, P=0.001). The most beneficial aspect was patient safety, while lack of patient

cooperation is the most common reason preventing clinicians from using the rubber dam.

Slawinski and Wilson (2010) assessed the use of rubber dam isolation by surveying the directors

of pediatric dentistry programs as well as private practice pediatric dentists in the US. From a

sample size of 75 program directors and 200 private practice pediatric dentists, 56 program

directors and 59 private practitioners responded. When asked if rubber dam usage was

emphasized in residency, 97% agreed which was more than those who currently use rubber dam

isolation today (83%) and consider it to be the standard of care. No significant difference was

seen between rubber dam usage and how many restorative procedures were completed on an

average day. The most common factors for using rubber dam isolation was; maintaining a dry

field (17%), minimizing salivary contamination (16%), aiding in visualization (16%), preventing

patient injury/aspiration (16%), increasing efficiency (15%), serving as a behavior management

adjunct (12%), and minimizing bacterial infection (9%). The most common reasons when rubber

dam is not used were; patient fear of suffocation (31%), potential painful stimulus (31%), allergy

(15%), time of application (8%), interference with operative care (8%), decreased efficiency

(3%), risk of injury (3%), and risk of funnelling fluids to the patient’s body (1%). Pulp therapy

was the procedure most likely to use the rubber dam isolation.

Overall, the use of a rubber dam is beneficial for the longevity of restorations as well as health

and safety of the patient and dental team; if able, all preparations should utilize the rubber dam

(Randall et al., 2000).

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2.11 Survey Tool

Surveys, both postal and web-based, are used in research to assess the knowledge, views, and

attitudes of health care professionals (Fawcett & Buhle, 1995; Braithwaite, Emery, De Lusignan,

& Sutton, 2003; Dillman, 2007). Although postal surveys have been traditionally used, web-

based health related research has increased exponentially in the past two decades (Duffy, 2002;

Cantrell & Lupinacci, 2007). With the capability to integrate images, sounds, and a graphic user

interface, the internet can create a more intuitive context for research opportunities (Duffy,

2002).

For the researcher, web-based surveys allow access to a specific population in a quick, cost

effective, and efficient manner (Duffy, 2002; Ahern, 2005). In comparison to traditional postal

surveys, the data collection period is dramatically reduced from a minimum of a four- to six-

week period to a minimum of a two to three-day period (Duffy, 2002). There is also an increased

ability to access a larger pool of study participants which allows for improved external reliability

and generalizability (Ahern, 2005; Cantrell & Lupinacci, 2007).

Greenlaw and Brown-Welty (2009) assessed the response rate and cost efficiency of postal

versus email/mixed mode survey distribution (Greenlaw & Brown-Welty, 2009). The web-based

survey had a higher response rate (52.46%) than the mail-based administration (42.03%) and was

less costly to administer at $0.64 USD/response versus a $4.78 USD/response (Greenlaw &

Brown-Welty, 2009). The conclusion of the study was that web-based administration is the better

choice for overall cost efficiency, while still allowing a good response rate (Greenlaw & Brown-

Welty, 2009). Once a web-based study is set up, it has a low cost to administer, allowing a

greater number of participants to be recruited and repeated data collection (Wyatt, 2000).

Internet surveys can prohibit multiple or blank responses by not allowing the participant to

continue without first correcting the response error (Schleyer & Forrest, 2000). By integrating

the research tool, there is an increase in efficiency of time, accuracy of the data entry and

analysis, and the ability to conduct follow-up studies (Ahern, 2005). Being able to link a web-

based survey directly to a database or spreadsheet application eliminates possible manual data

entry errors (Wyatt, 2000; Duffy, 2002). In addition, associated material such as data definitions

52

or protocols for the study can be linked, which will allow the participant to access more

information if they desire (Wyatt, 2000).

For the study participants, web-based research allows for convenience; ease of use, ability to

provide information at their own pace, an increased sense of control, and increased anonymity

(Fawcett & Buhle, 1995; Rosenstiel et al., 2004; Ahern, 2005). Web-based surveys still require

the protection of human subjects by anonymity, privacy, and confidentiality similar to postal

surveys (Eysenbach & Till, 2001; Ahern, 2005). However, the anonymity provided in an online

survey may allow for more truthfulness as it decreases social response bias and researcher

influenced bias, thereby enhancing the veracity of the data (Cantrell & Lupinacci, 2007).

Although the internet is a novel way to assess study populations, there are some disadvantages to

this mode of study (Ahern, 2005). The sample pool includes people who have access to a

computer which may lead to a better educated, technologically aware, and urban population,

thereby limiting generalizability (Daly, 2003; Ahern, 2005). In addition, there may be difficulty

with the equipment, network incompatibility, and survey error due to complex design (Duffy,

2002; Daly, 2003). The differences among computers such as memory, connection speeds, and

processing power may negate using more interactive graphics and animation (Schleyer &

Forrest, 2000). Errors that may reduce data validity include participants incompletely scrolling

down to see a whole page of questions or list of options in a list box or not understanding how to

correct a mistaken response (Wyatt, 2000). The ability to copy and paste may lead to new

patterns of responses that “fail to reflect true feelings” (Wyatt, 2000).

The web-based survey must be appropriately designed for data collection to ensure the quality of

internet data collected (Ahern, 2005). Analyzing a web-based survey is not the same as inputting

a paper survey as formatting may need to change to simplify data entry, clarify possible

responses, and avoid the possibility of submitting data before completing the survey (Braithwaite

et al., 2003). Pilot studies are just as important, if not more, versus paper surveys to ensure that

issues can be detected and corrected (Wyatt, 2000).

A high response rate from a sample is essential to be able to generalize the data to a population

(Parashos, Morgan, & Messer, 2005). According to Dillman, the response rates for the mail

survey treatment group and the e-mail treatment group were the same at 58%; however, the

53

responses to the email survey were more rapid (Dillman, 2007). It is the general opinion that

above 80% is an optimal response rate although lower response rates can be acceptable (Evans,

1991; Wyatt, 2000; Parashos et al., 2005). As web-based surveys are used more often, a

challenge is to prevent survey fatigue which may contribute to a poor response rate (Wyatt,

2000).

Parashos et al. (2005) reports that responders may include “more active and concerned segments

of the dental community,” which would change the results of the survey (Parashos et al., 2005).

An assumption of similar socio-demographic factors both between and within respondent and

non-respondent groups is made; however, non-responders in reality may have a different

perception (Parashos et al., 2005). Some reasons for non-responders may be lack of time, lack of

interest, working part time, being on holiday, and no specific reason (Parashos et al., 2005).

Overall, the web-based survey is a good modality to assess a large population with minimal cost

and time.

3 Objective of Thesis

In light of the issues alluded to above, this thesis is aimed to investigate the choice of direct

restorative material for primary and permanent molar restorations in healthy, developmentally

delayed, and medically compromised patients.

More specifically, the aims are as follows:

To assess material selection for direct restorative material by Pediatric Dentists in North

America for primary and permanent posterior teeth in normal healthy, developmentally

delayed, and medically compromised patients

To assess the factors that influence the practitioner’s decision to place a particular type of

material

To assess usage, indications, and contraindications for rubber dam isolation

To assess the preferred clinical decision making role that dentists prefer

To assess the response by Pediatric Dentists when concerns arise from caregivers about

the choice of direct restorative material

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4 Materials and Methods

4.1 Design

This study used a cross-sectional web-based survey approved by the University of Toronto

Research Ethics Board (Protocol No. 28490). Using the Dillman design (Dillman, 2007), a self-

administered online survey was conducted among all the active practicing members of the

American Academy of Pediatric Dentistry (AAPD) and Pediatric Fellows of the Royal College

of Dentists of Canada (RCDC). Participants were approached by a personalized introductory e-

mail which included the purpose of the research project, time needed, considerations for

informed consent such as anonymity and confidentiality, and methods to contact if questions

arise. A link to an online interface (Survey GizmoTM

, Colorado, USA) was given which

displayed the survey instrument (http://s-646bdf-i.edu.surveygizmo.com/s3/i-100157000-

393311/?sguid=100157000). Similar e-mails were repeated four times over six months. There

was no gift or remuneration provided to the participants.

4.2 Survey Instrument

The survey instrument was pilot-tested among fourteen Pediatric Dentistry residents and staff at

the Faculty of Dentistry, University of Toronto. Pilot testing aimed to evaluate the design, time

needed to respond, inclusion and exclusion of questions, ease of survey administration, and

feasibility of the planned data analysis. At the end of each page, the respondent was asked

follow-up questions to ensure ease of understanding and simplicity in answering. The survey was

finalized on the basis of three principal domains.

Domain 1 included; the practitioners’ gender, age range, years in practice, type of pediatric

dentistry training, current practice type, location of practice, average number of patients seen per

day, average number of patients receiving restorative treatment per day, demographic of patients,

and insurance acceptance.

Domain 2 included; eight scenarios about the preference of material (amalgam, composite,

compomer, glass ionomer, resin-modified glass ionomer, or stainless steel crown (SSC) used for

55

different restorations (Class I, II, and V) in primary and permanent teeth for three different

populations (healthy, medically compromised, and developmentally delayed individuals). The

type of material used most often for teeth with pulp therapy and large interproximal caries with

circumgingival decalcification was also included in the scenarios. We assumed that as the

number of recalls and treatment sessions increase, then the dentist is busier. Hence, for the

purpose of data analysis, we considered the busyness as follows: 0-9 recalls/day as ‘low’, 10-20

as ‘moderate’, and >20 as ‘high’. Similarly, we categorized the number of treatment sessions per

day as follows: 0-4 as ‘low’, 5-9 as ‘moderate’, 10-14 as ‘high’, and >15 as ‘very high’. All

scenarios emphasized that the patient’s behavior was acceptable, no sedation was required, and

there is no time constraint for treatment to be provided. In addition, the reasons for use of each

material were determined by assessing the scientific, tooth, and patient related factors. The

scientific factors include that the material; is supported by research/evidence based, is

historically safe and reliable, is primarily taught at school, has good mechanical properties, has

fewer steps to restore, allows for fluoride release, has lower toxicity than other materials, is less

allergenic, allows for a more conservative preparation, is esthetically pleasing. The tooth factors

include; the expected lifespan, a subgingival preparation margins, gross caries requiring a large

preparation, an inability to obtain proper isolation, after pulp treatment, bruxism. Finally, the

patient factors include; the patient’s age, affordability, caries risk assessment, poor oral hygiene,

poor patient behavior, if the caregivers insist. Rubber dam isolation was assessed in terms of

usage in primary and permanent teeth, indications, and contraindications.

Domain 3 included; the assessment of the preferred role in clinical decision making using the

Control Preferences Scale (CPS) (Degner, Sloan, & Venkatesh, 1997). The CPS is a validated

self-report measure of “the degree of control an individual wants to assume when decisions are

being made about medical treatment” (Degner et al., 1997). To determine the preferred role in

decision making about restorative material utilization, the participants were asked to choose their

preference from among five levels of participation in making the decision regarding selection of

the restorative material (Table 5.10). This domain also included the factors important to the

caregiver or patient in decision making using a four-point Likert scale (very important,

important, somewhat important, not important at all). These factors included; frequency of

questions asked by caregivers about restorative materials, changing of treatment plans secondary

to third party reimbursement, the frequency of caregivers creating pressure for a certain type of

56

treatment, and concerns about toxicity from caregivers. The ‘right answer’ involves further

discussion of the preference of the dentist with the patient/caregiver regarding the pros/cons/fees

associated with the various treatment options including no treatment (A) and/or referral to a

different practitioner (B). The ‘wrong answer’ was defined as placing the restoration that the

patient/caregiver prefers without further discussion (C) and having the patient/caregiver sign an

informed consent form about the restoration and its potential to fail without further discussion

(D).

4.3 Sample Size

The sample size (n) calculations were based on some assumptions:

A 5% margin of error as a maximum amount that could be tolerated for this population;

A 95% confidence interval to assess the levels of uncertainty to improve the rigor of the

investigation;

The AAPD and RCDC membership size of 4648 individuals;

A response distribution rate of 50% based on studies with a similar population.

An online sample size calculator (http://www.raosoft.com/samplesize.html) was used to

determine the sample size (n) of 355. In order to ensure generalizability of the results and the

recruitment of the adequate sample size, the survey was distributed to all members of the AAPD

and the Pediatric Fellows of the RCDC yielding a sample size of 4648.

4.4 Data Analysis

Data from the online survey was downloaded from the Survey GizmoTM

website to Microsoft

ExcelTM

and then into the statistical analysis software, SAS 9.3 (SAS Institute Inc, Cary, NC).

When assessing the materials individually, the frequency of responses for compomer, glass

ionomer, and resin-modified glass ionomer were minimal; these materials were grouped into a

category named “fluoride releasing restorations” to simplify data analysis. A descriptive analysis

of the data was undertaken.

57

a) To determine if the demographics affect the material selection, the Pearson Chi-square

test (or Fisher’s exact test as indicated) was utilized. The bivariate odds ratio (OR) of

associations were created to determine the association between the predictor variables

and all materials individually. In addition, the bivariate OR for the association between

amalgam and all other materials (compomer, composite, glass ionomer, resin-modified

glass ionomer, SSC) was also assessed. All variables that were significant in the bivariate

analyses were placed into multivariate correlation matrices to assess and explore any

correlations in predictor variables. The frequency of responses for each material in terms

of scientific, tooth, and patient factors was assessed.

b) For rubber dam isolation, the Pearson Chi-square test (or Fisher’s exact test as indicated)

evaluated the significance between usage and demographic predictor variables. Bivariate

and multivariate ORs for rubber dam usage and predictor variables were also assessed.

c) The responses to the CPS (Table 5.10) were categorized into active (choices A and B),

collaborative (choice C), or passive (choices D and E) roles for the respondents’ preferred

role in clinical decision making (Degner et al., 1997). Using the Likert scale, the

frequency of responses regarding the important factors for decision making was also

described. The Pearson Chi-square test (or Fisher’s exact test as indicated) was utilized to

assess significance between the preferred role in decision making and the predictor

variables. In addition, the frequency and the association between the predictor variables

and the type of response given after parental pressure were assessed using the Pearson

Chi-square (or Fisher’s exact test as indicated).

All tests were evaluated at the significance level of P<0.05 and were two-tailed.

58

5 Results

5.1 Descriptive Data

The response rates and a breakdown of the sample are presented in Figure 5.1. A sample of 4648

pediatric dentists with available email addresses were acquired from the AAPD and the RCDC

membership lists. Of the total sent, 660 emails were bounced back, thus yielding an active list of

3988 respondents. After three reminder emails, 37 people unsubscribed, leading to a total of

3951 respondents. There were 762 partial and complete responses which reflected a response rate

of 19.3%.

The demographic characteristics of survey participants are summarized in Table 5.1. The

majority of the participants are; from the United States of America (USA) (90%) and the east

coast (49.8%), obtained a pediatric dentistry diploma (77.1%) in a combined hospital and

university setting (63.6%), work in private practice (87.4%), accept government funding

(71.9%), and have 0-10 years of experience (41.8%). About half of the participants see twenty or

more recall and hygiene patients (51.7%) per day and perform five to nine restorative treatments

(47%) per day.

59

Figure 5.1- Response Rates for Pediatric Dentists Web-based Survey

The table shows that in the pool of 3951 Pediatric Dentists in Canada and the United States of

America with valid email addresses, a total of 762 usable surveys were collected. This reflected a

response rate of 19.3%.

4648 Pediatric Dentists

Active List:

4648-660-37= 3951

660 bounced back

emails

37 unsubscribed

762 started the survey

Final number of

surveys= 762

Response rate: 19.3%

689 USA respondents

73 Canadian

60

Table 5.1- Descriptive Results of Survey Participants

Variables Frequency (n) Percentage (%)

(%) (( (%) Gender (male) 375 51.2

Country USA 661 90.1

Canada 73 10.0

Location West 158 22.5

Central 195 27.7

East 350 49.8

Type of training Diploma/Certificate 571 77.1

MSc/PhD 148 20.6

Other 22 3.0

Settings Hospital-based 180 24.4

University-based 88 11.9

Combined 469 63.6

Primary practice Private 589 87.4

Academic/hospital 60 8.9

Public funded 25 3.7

Government fund 528 71.9

Years of Experience 0-10 309 41.8

11-20 180 23.4

20+ 250 33.8

Number of Recalls per day 0-9 115 15.8

10-19 236 32.5

20+ 375 51.7

Number of treatment per day

0-4 92 12.7

5-9 340 47.0

10-14 202 27. 9

15+ 90 12.4

5.2 Current usage of direct restorative materials

Figure 5.2 and Table 5.2 show the general pattern of increased usage of composite resin in

primary and permanent Class I, II, and V restorations in healthy and medically compromised

individuals in this sample population. Figure 5.2 visually represents the higher frequency of

composite usage in healthy and medically compromised patients for both primary and permanent

teeth. For developmentally delayed patients, stainless steel crowns are used most often in

primary teeth and a similar frequency of amalgam and composite is used for the permanent teeth.

Table 5.3 displays the bivariate and final multivariate association between the predictor variables

and the choice of types of restorations. The final multivariate model shows that composite was

61

selected less often than amalgam for medically compromised (OR 0.62; CI 0.63-0.71) or

developmentally delayed patients (OR 0.19; CI 0.15-0.23) as compared to otherwise healthy

patients, Class II restorations as compared to Class I restorations (OR 0.65; CI 0.58-0.73),

Canadian pediatric dentists as compared to American pediatric dentists (OR 0.54; CI 0.32-0.91),

those who had their specialty training in academic or hospital settings as compared to those with

combined training (OR 0.48; CI 0.27-0.86), those who accept government funded patients as

compared to those who do not (OR 0.47; CI 0.300.73), those with a moderate number of recalls

per day compared to those with a high number (OR 0.67; CI 0.45-0.97).

Figure 5.2- Restorative Material Choice for Healthy, Medically compromised (MC), and

Developmentally Delayed (DD) Patients

62

Table 5.2: Restorative Material Choice for Class I, II, and V Restorations in Primary and

Permanent teeth

Amalgam Composite Compomer Glass

ionomer

Resin-

Modified

Glass

ionomer

Stainless

steel

crown

(%) (%) (%) (%) (%) (%)

Primary Right Md 1st

Molar Class I

Healthy 12.6 52.1 7.9 3.0 7.2 17.2

MC 13.4 41.7 7.7 2.9 7.8 26.6

DD 16.7 22.0 5.5 6.7 10.7 38.4

Primary Right Md 1st

molar Class V

Healthy 8.5 47.5 7.3 5.4 10.0 21.3

MC 9.2 36.3 7.0 4.5 10.1 32.9

DD 12.6 17.5 4.9 7.9 12.4 44.7

Primary Right Md 2nd

Molar Class II

Healthy 17.3 51.3 8.4 3.2 9.0 10.8

MC 16.6 36.6 8.4 2.3 7.5 28.6

DD 17.9 16.8 5.0 4.7 8.7 46.9

Permanent Right Md

1st Molar Class I

Healthy 12.0 83.4 1.7 0.5 2.2 0.2

MC 21.1 71.1 2.6 0.8 3.9 0.6

DD 40.2 38.2 2.7 3.2 10.8 5.0

Permanent Right Md

1st molar Class V

Healthy 10.0 79.0 2.2 2.4 6.2 0.2

MC 17.0 67.7 2.6 4.2 7.8 0.8

DD 34.1 35.5 3.2 6.6 15.0 5.5

Permanent Right Md

2nd Molar Class II

Healthy 21.9 74.3 1.3 0.3 2.0 0.2

MC 29.4 62.4 1.9 0.6 4.0 1.7

DD 44.2 33.5 2.1 2.3 9.3 8.6

Fluoride releasing restorations versus amalgam

Fluoride releasing restorations were chosen less than amalgam in permanent teeth as compared

to primary teeth (OR 0.30; CI 0.24-0.38), for Class II as compared to Class I restorations (OR

0.69; CI 0.61-0.79), if the practitioner has a MSc/PhD compared to a diploma (OR 0.43; CI 0.25-

0.74), by those whose primary practice is in academic or hospital settings compared to private

practice (OR 0.41; CI 0.21-0.80), by those who accept government funded patients compared to

those who do not (OR 0.41; CI 0.24-0.69), and by those who see a low number of recalls per day

63

compared to those who see a high number of recalls (OR 0.45; 0.22-0.92). The participants

reported to use fluoride releasing restorations more often than amalgam for Class V compared to

Class I restorations (OR 1.73; CI 1.51-1.98).

SSC versus amalgam

The participants reported to use SSC more than amalgam for medically compromised (OR =1.61;

CI 1.36-1.91) or developmentally delayed patients (OR=2.06; CI 1.66-2.55) as compared to

otherwise healthy patients, and for Class V restorations (OR 1.63; CI 1.43-1.85) as compared to

Class I restorations. However, SSC was reported to be used less often than amalgam in

permanent teeth compared to primary teeth (OR 0.04; CI 0.03-0.06), for Class II restorations

(OR 0.82; CI 0.67-0.99) compared to Class I restorations, with each additional year of

experience (OR 0.97; CI 0.95-0.99), by those who have a low number of recalls per day as

compared to high (OR 0.5; CI 0.27-0.95), by those who see a moderate number of recalls per day

as compared to high (OR 0.5; CI 0.33-0.76).

Amalgam usage versus all other materials

Using multivariate analysis to assess the use of amalgam versus all other materials (Table 5.4),

amalgam was preferred more often for medically compromised (OR= 1.36 CI 1.22-1.54) or

developmentally delayed patients (OR=2.56; CI 2.17-2.94) in comparison to otherwise healthy

patients, for permanent teeth (OR= 2.17; CI 1.85-2.56) in comparison to primary teeth, for Class

II restorations (OR 1.41; CI 1.27-1.54) in comparison to Class I restorations, by those who

accept government funding (OR 2.04; CI 1.43-2.94) in comparison to private practice

practitioners, by practitioners who see a low number of recalls per day in comparison to a high

number (OR= 2.13; CI 1.43-3.12), by those that see a moderate number of recalls in comparison

to high (OR 1.96; CI 1.44-2.70). Other materials were preferred over amalgam for a Class V

restoration in comparison to a Class I restoration (OR 0.73; CI 0.67-0.81).

64

Table 5.3: Univariate and Multivariate OR (95% CI) comparing the use of Composite, Fluoride releasing restorations, and Stainless

steel crowns (SSC) vs Amalgam Factor Level Univariate OR (95% CI) Multivariate OR (95% CI)

Composite F releasing resto SSC Composite F releasing resto SSC

Health status

Ref: Healthy

MC

DD

0.64(0.56,0.73)

0.21(0.17,0.25)

0.82(0.70,0.96)

0.69(0.56,0.86)

1.42(1.21,1.67)

1.44(1.18,1.77)

0.62(0.53,0.71)

0.19(0.15,0.23)

0.86(0.72,1.01)

0.80(0.64,1.01) 1.61(1.36,1.91)

2.06(1.66,2.55)

Tooth type

Ref: Primary

Permanent 0.97(0.81,1.17) 0.29(0.23,0.36) 0.05(0.04,0.08) 1.17(0.97,1.41) 0.30(0.24,0.38) 0.04(0.03,0.06)

Restorative class

Ref: Class I

Class V

Class II 1.10(1.01,1.21)

0.69(0.62,0.77)

1.61(1.42,1.83)

0.73(0.65,0.82)

1.45(1.30,1.63)

0.85(0.72,1.00)

1.11(1,1.22)

0.65(0.58,0.73)

1.73(1.51,1.98)

0.69(0.61,0.79)

1.63(1.43,1.85)

0.82(0.67,0.99)

Gender

Ref: male

Female 1.05(0.75,1.46) 0.99(0.65,1.51) 1.21(0.87,1.69)

Years of experience Each

additional year

1.00(0.98,1.01) 1.01(0.99,1.03) 0.97(0.96,0.99) 1.00(0.98,1.01) 1.01(0.99,1.03) 0.97(0.95,0.99)

Country

Ref: USA

Canada 0.44(0.28,0.69) 0.43(0.22,0.83) 0.81(0.52,1.26) 0.54(0.32,0.91) 0.80(0.40,1.62) 1.18(0.66,2.12)

Location

Ref: East

West

Central

0.92(0.60,1.41)

0.69(0.47,1.02)

1.07(0.63,1.83)

0.79(0.48,1.29)

0.98(0.63,1.54)

1.03(0.71,1.50)

Type of Training

Ref: diploma

MSc/PhD 0.72(0.49,1.06) 0.36(0.21,0.61) 1.00(0.69,1.45) 0.95(0.63,1.43) 0.43(0.25,0.74) 0.99(0.63,1.55)

Setting of Training

Ref: University

Combined

Hospital

1.12(0.64,1.94)

1.36(0.75,2.49)

0.91(0.47,1.75)

0.85(0.41,1.77) 1.77(1.04,2.99)

1.40(0.78,2.53)

Current primary

practice

Ref: Private

Acad/hosp

Public 0.34(0.19,0.60)

0.42(0.21,0.87)

0.22(0.11,0.44)

0.97(0.40,2.33)

0.75(0.46,1.23)

0.65(0.32,1.33) 0.48(0.27,0.86)

0.66(0.28,1.56) 0.41(0.21,0.8)

2.06(0.72,5.89)

1.25(0.69,2.26)

1.17(0.44,3.10)

Gov’t fund

Ref: No

Yes 0.45(0.30,0.68) 0.36(0.22,0.60) 1.09(0.69,1.71) 0.47(0.3,0.73) 0.41(0.24,0.69) 1.09(0.67,1.78)

Number of

recalls per day

Ref: 20+

0-9

10-20 0.43(0.28,0.68)

0.60(0.41,0.87)

0.38(0.21,0.67)

0.59(0.37,0.95)

0.57(0.36,0.89)

0.51(0.35,0.74)

0.61(0.35,1.07)

0.67(0.45,0.97)

0.45(0.22,0.92)

0.66(0.41,1.06) 0.50(0.27,0.95)

0.50(0.33,0.76)

Number of

treatments

per day

Ref: 5-9

0-4

10-14

15+

0.96(0.59,1.56)

0.90(0.51,1.59)

1.13(0.77,1.67)

0.89(0.48,1.64)

0.99(0.49,1.98)

0.72(0.43,1.20)

0.95(0.57,1.57)

0.92(0.53,1.61)

1.07(0.72,1.58)

*Reference: Amalgam

*Abbreviations above: MC= medically compromised, DD= developmentally delayed, acad = academic hosp= hospital, gov’t= government

65

Table 5.4: Univariate and Multivariate OR (95% CI) for the combined use of all other materials

vs Amalgam

All other materials vs amalgam Amalgam vs. all other materials

Factor Level Univariate

Odds Ratio

(95%CI)

Multivariate

Odds Ratio

(95%CI)

Univariate

Odds Ratio

(95%CI)

Multivariate

Odds Ratio –

(95%CI)

Health status

Ref: Healthy

MC

DD

0.74 (0.66, 0.83)

0.42 (0.37, 0.49) 0.73 (0.65, 0.82)

0.39 (0.34, 0.46)

1.35 (1.21, 1.51)

2.36 (2.04, 2.73) 1.38 (1.23, 1.55)

2.54 (2.17, 2.97)

Tooth type

Ref: Primary

Permanent 0.51 (0.42, 0.61) 0.46 (0.39, 0.54) 2.09 (1.79, 2.45) 2.19 (1.85, 2.60)

Restorative class

Ref: Class I

Class V

Class II

1.26 (1.15, 1.38)

0.72 (0.65, 0.80) 1.36 (1.24, 1.49)

0.71 (0.65, 0.79)

0.75 (0.69, 0.82)

1.36 (1.25, 1.49) 0.74 (0.67, 0.81)

1.40 (1.27, 1.54)

Gender

Ref: male

Female 1.06 (0.78, 1.45) 1.02 (0.78, 1.33)

Years of

experience

Every

year

1.00 (0.98, 1.01) 1.00 (0.99, 1.01)

Country

Ref: USA

CA 0.50 (0.33, 0.76) 1.74 (1.19, 2.55)

Location

Ref: East

West

Central

0.94 (0.64, 1.40)

0.77 (0.54, 1.10)

1.10 (0.77, 1.57)

1.40 (1.02, 1.92)

Type of Training

Ref: diploma

MSc/PhD 0.68 (0.48, 0.97) 1.31 (0.95, 1.80)

Setting of

Training

Ref: University

Combined

Hospital

1.12 (0.67, 1.88)

1.18 (0.68, 2.07)

0.79 (0.50, 1.27)

0.78 (0.51, 1.19)

Current primary

practice

Ref: Private

Acad/hosp

Public

0.39 (0.24, 0.61)

0.58 (0.32, 1.04)

2.40 (1.60, 3.61)

1.51 (0.85, 2.68)

Gov’t fund

Ref: No

Yes 0.52 (0.37, 0.73) 0.49 (0.34, 0.70) 1.93 (1.38, 2.71) 2.04(1.42-2.94)

Number of

recalls per day

Ref: 20+

0-9

10-20

0.45 (0.29, 0.68)

0.58 (0.41, 0.82) 0.47 (0.32, 0.70)

0.51 (0.37, 0.69)

2.00 (1.39, 2.88)

1.82 (1.36, 2.44) 2.12(1.43-3.13)

1.96(1.45-2.70)

Number of

treatments

per day

Ref: 5-9

0-4

10-14

15+

0.93 (0.60, 1.45)

1.03 (0.71, 1.48)

0.92 (0.54, 1.57)

1.02 (0.69, 1.50)

1.06 (0.77, 1.47)

1.12 (0.72, 1.74)

5.2.1 Factors Associated with Choice of Material

The scientific, tooth, and patient factors associated with the choice of each material are

summarized in Table 5.5. The scientific factors most associated with amalgam include;

supported by research/evidence based (61.1%), historically safe and reliable (62.2%), primarily

taught at school (60.2%), good mechanical properties (58%), and fewer steps to restore (52.7%).

In comparison, composite resin also had similar responses as it is reported to be evidence based

66

(76.9%), historically safe and reliable (62.9%), primarily taught at school (57.2%), and has good

mechanical properties (57.2%). When comparing tooth factors, the expected lifespan of the tooth

was deemed most important for SSC (81%), composite (64.7%), and amalgam (49.7%). When

the tooth has sub-gingival margins, gross caries, and difficulty to obtain proper isolation, SSC

was chosen to be an appropriate restorative material (85.5%, 95.1%, and 73.7% respectively).

For affordability, amalgam had the highest response (64.7%) in comparison to composite

(41.3%) and SSC (43.9%). Poor oral hygiene is a factor when restoring with amalgam (45.9%)

or SSC (90.6%). Composite (12.7%) and compomer (5.4%) are not used often when there is poor

patient behavior. Caregivers pressure dentists to place composite (91.4%) the most often in

comparison to the other materials. With the exception of a few reasons (esthetics, allow for

fluoride release, allow for a conservative preparation, affordable, and caregivers insistence), the

participants selected the investigated factors in Table 5.5 with a high frequency for the SSC.

67

Table 5.5: The Scientific, Tooth, and Patient related Factors which contribute to the Reason for

Using each Restorative Material

Amalgam

(%)

Compomer

(%)

Composite

(%)

Glass

ionomer

(%)

Resin-

modified

glass

ionomer

(%)

Stainless

steel

crown

(%)

Scientific

Factors

Supported by

research/ evidence

based

61.1 18.6 76.9 42.5 45.2 92.3

Historically safe and

reliable 62.2 12.9 62.9 29.3 30.9 89.4

Primarily taught at

school 60.2 7.5 57.2 19.3 19.9 86.4

Good mechanical

properties 58.0 12.6 57.2 14.6 24.7 81.4

Fewer steps to restore 52.7 5.5 8.1 29.8 27.4 66.1

Allows for fluoride

release 0.0 19.7 6.0 74.5 70.7 0.4

Lower toxicity than

other materials 8.2 13.1 35.9 38.2 32.1 79.6

Less allergenic 22.3 14.6 48.1 41.8 35.2 51.9

Allows for a

conservative

preparation

3.7 25.0 91.2 42.1 45.3 2.2

Esthetically pleasing 0.4 26.8 95.8 27.7 37.9 0.9

Tooth

Factors

Expected lifespan 49.7 17.1 64.7 30.0 36.8 81.0

Subgingival

preparation margins 44.0 2.7 5.8 23.3 22.4 85.5

Gross caries

requiring a large

preparation

21.9 2.3 12.4 8.8 9.7 95.1

Inability to obtain

proper isolation 54.2 2.9 2.6 33.9 25.0 73.7

After pulp treatment 4.9 3.5 9.2 3.3 4.4 97.2

Bruxism 27.8 7.1 28.2 7.7 11.3 82.3

Patient

Factors

Patient's age 45.7 14.4 69.3 35.1 39.5 86.7

Affordable 64.7 10.3 41.3 19.8 19.1 43.9

Based on caries risk

assessment 42.9 13.2 45.5 36.2 37.9 89.3

Poor oral hygiene 45.9 5.6 14.3 27.8 27.7 90.6

Poor patient behavior 43.6 5.4 12.7 29.3 27.1 77.6

Caregivers insist 16.0 12.9 91.4 14.9 19.0 12.2

68

5.3 Rubber Dam Usage

Table 5.6 shows the distribution of participants who use rubber dam isolation, and the factors

that would affect their responses. In total, 72.5% of the participants reported using rubber dam

isolation ‘all the time’, 16.6% ‘sometimes’, and 10.8% ‘never’. In particular, Canadian

respondents, those who practice in west or central regions, those with MSc/PhD training, those

who practice primarily in academic or hospital setting, those who accept government funding,

and those with moderate number of recalls (10-19) and treatment (5-9) per day had the highest

frequency for the use of rubber dam. Having controlled for these significant variables (Table

5.7), we found that those with the most number of recalls per day (>20) are almost 2 times less

likely to use rubber dam as compared to those with moderate number of recalls of 10-19 per day

(OR=2.26, 95% CI: 1.19-4.32).

For the respondents who use rubber dam isolation, the vast majority use it for all materials in the

primary (97.5%) and permanent dentition (96%). The material with the lowest rubber dam usage

was composite (82.2%) in the primary dentition and SSC (81.9%) in the permanent dentition.

The main reason for using rubber dam isolation was moisture control through isolation (94%),

followed by; better view with retraction of soft tissue (89.5%), poor behavior (45.5%), large

preparation (35%), and other (28.6%). The reasons for not using rubber dam isolation include;

decreased trauma to the patient (65%), other methods to retract soft tissue (55%), decreased time

for appointments (45%), the material used does not require a dry field (13.2%), the practitioner

can achieve better isolation without the use of a rubber dam (13.2%), and other (33.8%).

69

Table 5.6: The Factors associated with the Use of Rubber Dam Isolation

Don’t use

n (%)

Use

n (%)

P value

Total 69(10.8) 568 (89.1)

Gender Female 35(11.5) 270(88.5) 0.68

Male 34(10.5) 291(89.5)

Years of Experience 0-10 31(11.7) 233(88.3) 0.40

11-20 19(12.7) 131(87.3)

20+ 19(8.6) 201(91.4)

Country CA 0(0.0) 67(100.0) <0.01*

US 69(12.3) 493(87.7)

Location West 10(7.8) 118(92.2) 0.04

Central 13(7.6) 158(92.4)

East 41(14.1) 250(85.9)

Type of training Diploma 60(12.4) 425(87.6) 0.05

MSc/PhD 8(6.2) 121(93.8)

Settings Hospital-based 17(11.1) 136(88.9) 0.47

University-based 5(6.8) 69(93.2)

Combined 47(11.6) 359(88.4)

Primary practice Private 62(12.3) 444(87.7) 0.04*

Acad/Hosp-based 0(0.0) 52(100)

Public funded 2(9.5) 19(90.5)

Government fund Yes 42(9.2) 415(90.8) 0.03

No 27(15.0) 153(85.0)

Number of Recalls per

day

0-9 10(9.4) 96(90.6) 0.03

10-19 13(6.5) 186(93.5)

20+ 45(13.9) 280(86.1)

Number of treatment per

day

0-4 11(12.8) 75(87.2) 0.80

5-9 27(9.5) 257(90.5)

10-14 21(11.6) 160(88.4)

15+ 9(11.5) 69(88.5)

Significance was assessed by Pearson Chi-square test

* Significance was assessed by Fisher’s exact test

Table 5.7: Multivariate Odds ratio (95% CI) for Rubber Dam Usage

Covariate OR 95% CI

Lower limit Upper limit

Number of Recalls per day 0-9 vs. 20+ 1.81 0.82 3.99

10-19 vs. 20+ 2.26 1.19 4.32

Government fund Yes vs. No 1.72 1.00 2.95

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5.4 Dentists’ Role in Determining Restorative Material Choice

Table 5.8 shows the proportions of the participants’ responses in the Controlled Preference Scale

for choice of restorative material. Over half of the participants preferred to have an active role (A

and B, 58.3%) while a third preferred a collaborative (C; 35.4%) and very few preferred a

passive role (D and E; 6.4%). Bivariate analyses are reported in Table 5.9 and show that

American paediatric dentists and those who practice in a university setting tend to prefer a less

active role. Having controlled for these significant variables (Table 5.10), active roles are chosen

about 2 times more by female than male pediatric dentists (OR= 1.88; 95% CI 1.17-3.01), by

those who live in eastern compared to central regions (OR =1.75, 95% CI 1.03-3.03), by those

who seldom or never have pressure from parents compared to those who sometimes have

pressure (OR=1.83, 95% CI 1.14-2.95). The passive role is chosen; 5 times more often for

Canadian than American pediatric dentists (OR 4.76, 95% CI 1.19-19.07), and more than 3 times

more often for those who work in a hospital-based setting compared to a combined setting (OR

3.15, 95% CI 1.13-8.79), and for those who work in a university based setting compared to a

combined setting (OR 3.61, 95% CI 1.11-11.77).

Table 5.8: Dentists Preferred Level of Participation in Clinical Decision Making for

Restorative Material Choice (N- 571)

Role Percentage

(%)

Questions Percentage

(%)

Active: The dentist decides

which treatment option would

be the most appropriate

58.3% A: I prefer to have the final decision of

which treatment my patient will

receive

11.7%

B: I prefer to make the final selection

of the treatment provided considering

my patients/caregiver opinion

46.6%

Collaborative: shared decision

making between the dentist

and the patient

35.4% C: I prefer that the patient/caregiver

and I collaboratively made the decision

35.4%

Passive: the patient decides

which treatment option would

be the most appropriate

6.4% D: I prefer that the patient/caregiver

makes the final decision but seriously

consider my opinion

6.0%

E: I prefer that the patient/caregiver 0.4%

71

makes the decision

Table 5.9: The Factors Associated with the Dentists’ Role in Decision-making for Material Choice

Active

n (%)

Collaborative

n (%)

Passive

n (%)

P value

Total Total Total

Gender Female 175(62.3) 91(32.4) 15(5.3) 0.24

Male 157(55.5) 106(37.5) 20(7.1)

Years of Experience 0-10 134(56.8) 89(37.7) 13(5.5) 0.66

11-20 74(56.1) 48(36.4) 10(7.6)

20+ 125(62.2) 64(31.8) 12(6.0)

Country CA 36(55.4) 20(30.8) 9(13.8) 0.03

US 294(58.9) 178(35.7) 27(5.4)

Location West 60(53.1) 46(40.7) 7(6.2) 0.12

Central 86(54.1) 60(37.7) 13(8.2)

East 167(64.7) 76(29.5) 15(5.8)

Type of training Diploma 255(58.5) 153(35.1) 28(6.4) 0.90

MSc/PhD 65(56.5) 43(37.4) 7(6.1)

Settings Hospital-based 84(62.2) 40(29.6) 11(8.2) 0.02

University-based 35(50.7) 25(36.2) 9(13.1)

Combined 213(58.5) 136(37.4) 15(4.1)

Primary practice Private 259(57.8) 159(35.5) 30(6.7) 0.46*

Acad/Hosp-based 26(54.2) 20(41.7) 2(4.2)

Public funded 16(76.2) 5(23.8) 0(0)

Government fund Yes 231(56.3) 151(36.8) 28(6.8) 0.29

No 102(63.3) 51(31.7) 8(5.0)

Number of Recalls per

day

0-9 61(62.2) 31(31.6) 6(6.1) 0.44

10-19 98(53.3) 75(40.8) 11(6.0)

20+ 172(60.8) 93(32.9) 18(6.4)

Number of treatment

per day

0-4 36(46.8) 35(45.4) 6(7.8) 0.26

5-9 159(62.3) 83(32.6) 13(5.1)

10-14 91(56.9) 56(35.0) 13(8.1)

15+ 44(61.1) 25(34.7) 3(4.2)

Significance was assessed by Pearson Chi-square test

* Significance was assessed by Fisher’s exact test

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Table 5.10: Multinomial Regression for Active and Passive Participation Preferences Compared

with Collaborative Participation

Active vs

collaborative

Passive vs

collaborative

Multivariate OR

(95% CI)

Multivariate OR

(95% CI)

Gender Ref: Male Female 1.88(1.17,3.01) 1.47(0.56,3.82)

Years of Experience

Ref: 11-20

0-10 0.59(0.34,1.00) 0.66(0.21,2.07)

20+ 0.68(0.37,1.23) 1.21(0.37,4.00)

Country

Ref: US

CA 1.53(0.72,3.26) 4.76(1.19,19.07)

Location

Ref: East

West 0.57(0.32,1.00) 0.63(0.20,2.02)

Central 0.57(0.33,0.97) 0.61(0.19,1.93)

Type of training

Ref: Diploma

MSc/PhD 0.83(0.48,1.43) 0.53(0.16,1.82)

Settings

Ref: Combined

Hospital-based 1.07(0.64,1.81) 3.15(1.13,8.79)

University-based 0.89(0.44,1.82) 3.61(1.11,11.77)

Primary practice

Ref: Private

Acad/Hosp - based 0.98(0.43,2.21) 0.21(0.02,1.96)

Public funded 1.32(0.35,4.92) NA

Government fund

Ref: No

Yes 0.63(0.38,1.05) 1.19(0.42,3.35)

Number of Recalls per

day

Ref: 20 +

0-9 1.59(0.72,3.51) 1.31(0.31,5.57)

10-19 0.66(0.40,1.11) 0.57(0.20,1.67)

Number of treatment

per day

Ref: 5-9

0-4 0.56(0.28,1.12) 1.66(0.44,6.21)

10-14 0.82(0.48,1.39) 1.12(0.40,3.13)

15+ 0.82(0.4,1.69) 0.39(0.07,2.22)

Pressure from patients

Ref: Sometimes

All/most time 1.40(0.6,3.24) 2.68(0.73,9.87)

Seldom/never 1.83(1.14,2.95) 1.38(0.52,2.69)

5.4.1 Factors associated with Decision-Making

Table 5.11 shows the importance of certain factors for treatment plan decision making. ‘Very

important’ factors include; communication and trust between the caregiver and dentist (94.7%),

patients’ previous experience related to different treatment options (58.6%), out of pocket

expense (45.7%), insurance coverage (43.9%), and fear of painful procedure (50.8%). Other

factors that were deemed as ‘important’ include; the number of treatment sessions (48.2%),

esthetic outcome (46.7%), probable longevity until failure (42.4%), and the consequences of

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failure (37.5%). The cost of maintaining the restoration was split between ‘very important’

(24.6%), ‘important’ (35%), and ‘somewhat important’ (31.6%). The factor that was most

frequently deemed ‘not important at all’ was fluoride (27.8%).

Table 5.11: The Relative Importance of Factors for Material Choice Decision-Making

Very

important

(%)

Important

(%)

Somewhat

important

(%)

Not

important at

all (%)

Communication and trust between

caregivers and dentist 94.7 5.3 0.0 0.0

Patients' previous experience

related to different treatment

options

58.6 30.9 10.1 0.5

Out of pocket expense to cover

the cost of treatment 45.7 40.4 11.5 2.5

Insurance coverage to cover cost

of treatment 43.9 36.9 15.0 4.2

Cost of maintaining the

restoration 24.6 35.0 31.6 8.8

Complexity of restorative

treatment necessary 26.2 34.9 27.8 11.1

Number of treatment sessions

required 35.2 48.2 14.5 2.1

Fear of a painful procedure 50.8 35.4 11.3 2.5

Esthetic outcome 38.1 46.7 14.6 0.5

Allows for fluoride release (caries

prevention) 8.9 19.9 43.4 27.8

Probable longevity until failure 36.0 42.4 18.7 2.9

Consequences of failure 32.2 37.5 27.0 3.2

5.4.2 Toxicity Concern and Response

For frequency of caregiver concerns about the type of restorative material used, the highest

proportion of responses were ‘most of the time’ (43.8%) and ‘seldom’ (46.2%; data not shown).

74

The survey respondent was able to choose more than one response about how he or she would

address pressure from the caregiver. There were three responses that were the most frequently

chosen; have the parents’ sign an informed consent (43.8%), refer to a different practitioner

(35.4%), try to convince the caregiver to use his or her preferred restoration (33.3%) (Table

5.12). Only 6.1% would place the restoration that the caregiver prefers. The right answer for the

response by the dentist to the caregiver after given pressure about material choice was chosen by

68.7%. This answer was chosen more often; by males (65.9%) than females (55.9%)(P<0.02;

Table 5.13). In addition, if the respondent was pressured “all/most of the time”, the right answer

was chosen less often (35.7%), than if he was pressured “sometimes” (62%), or “seldom/never”

(65.3%). Multivariate analysis shows that the wrong answer is chosen; more often by female

respondents in comparison to male (P=0.01), if the respondent mainly works in primary practice

in comparison to an academic or hospital based practice (P= 0.05), if the respondent receives

pressure from patients or caregivers about material choice all the time in comparison to

sometimes (P=0.02) (Table 5.13).

Respondents report that caregivers express concern about mercury toxicity “often” (9.6%),

“sometimes” (26.2%), and never (2.8%). Of the respondents, 32.8% reported that he or she does

not use amalgam. If amalgam is used and concerns arise, the vast majority (94%) would discuss

the evidence about the low mercury release from amalgams to change the caregivers’ opinion.

Table 5.12: Type of Response by Dentist to Caregiver after Caregiver Pressure about

Material Choice (n=559)

Type of Answer Percentage

(%)

Questions Percentage

(%)

Right answer: the correct

response when given pressure

by a caregiver

68.7% A: Continue trying to convince the

caregiver about the restoration you prefer

33.3%

B: Refer the patient to a different

practitioner

35.4%

Wrong Answer: the wrong

response when given pressure

by a caregiver

49.9% C: Place the restoration the parents prefer

6.1%

D: Have the parents sign an informed

consent about the restoration and its

potential to fail

43.8%

75

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Table 5.13: Treatment Provided Under Pressure from the Caregiver

Wrong answer

n (%)

Right answer

n (%)

P value Univariate OR

(95% CI)

P value Multivariate OR

(95% CI)

P value

Gender

Ref: Male

Female 123(44.1) 156(55.9) 0.02 1.53 (1.08, 2.15) 0.02 1.77(1.13,2.76) 0.01

Male 93(34.1) 180(65.9) 1.0 1.0

Years of Experience

Ref: 20 +

0-10 95(41.1) 136(58.9) 0.52 1.25 (0.85, 1.85) 0.52 0.98(0.59,1.63) 0.99

11-20 51(39.8) 77(60.2) 1.19 (0.75, 1.87) 0.98(0.56,1.72)

20+ 71(35.9) 127(64.1) 1.0 1.0

Country

Ref: US

US 191(39.1) 297(60.9) 0.82 1.0 0.82 1.0 0.14

CA 26(40.6) 38(59.4) 1.06 (0.63, 1.81) 1.71(0.83,3.51)

Location

Ref: East

West 43(38.7) 68(61.3) 0.70 0.89 (0.56, 1.40) 0.70 0.85(0.49,1.47) 0.19

Central 59(37.6) 98(62.4) 0.85 (0.56, 1.27) 0.62(0.37,1.04)

East 104(41.6) 146(58.4) 1.0 1.0

Type of training

Ref: Diploma

Diploma 164(38.54) 262(61.5) 0.80 1.0 0.80 1.0 0.35

MSc/PhD 42(37.2) 71(62.8) 0.95 (0.62, 1.45) 0.78(0.46,1.32)

Settings

Ref: Combined

Hospital-based 51(38.4) 82(61.6) 0.50 1.02 (0.68, 1.54) 0.50 0.93(0.57,1.52) 0.53

University-based 30(45.5) 36(54.5) 1.37 (0.81, 2.33) 1.42(0.73,2.74)

Combined 135(37.8) 222(62.2) 1.0 1.0

Primary practice

Ref: Acad/hosp-based

Private 169(38.2) 273(61.8) 0.10 1.55 (0.85, 2.83) 0.10 2.09(0.94,4.62) 0.05

Acad/Hosp-based 23 (48.9) 24 (51.1) 1.0 1.0

Public funded 11(57.9) 8(42.1) 2.22 (0.88, 5.63) 3.22(0.97,10.64)

Government fund

Ref: No

Yes 159(39.4) 245(60.6) 0.56 1.06 (0.72, 1.55) 0.78 0.99(0.61,1.59) 0.96

No 59(38.1) 96(61.9) 1.0 1.0

Number of Recalls per

day

Ref: 20+

0-9 37(38.5) 59(61.5) 0.50 0.89 (0.56, 1.43) 0.50 0.72(0.35,1.45) 0.30

10-19 63(35.8) 113(64.2) 0.79 (0.54, 1.17) 0.68(0.41,1.12)

20+ 116(41.3) 165(58.7) 1.0 1.0

Number of treatment

per day

Ref: 5-9

0-4 26(34.2) 50(65.8) 0.71 0.82 (0.48, 1.40) 0.70 0.47(0.23,0.95) 0.18

5-9 97(38.8) 153(61.2) 1.0 1.0

10-14 64(41.0) 92(59.0) 1.18 (0.69, 2.03) 1.05(0.63,1.73)

15+ 30(42.9) 40(57.1) 1.10 (0.73, 1.65) 1.15(0.58,2.28)

Pressure from patients

Ref: Sometimes

All/most time 27(64.3) 15(35.7) <0.01 2.93 (1.50, 5.71) <0.01 2.7(1.26,5.8) 0.02

Sometimes 132(38.0) 215(62.0) 1.0 1.0

Seldom/never 59(34.7) 111(65.3) 0.87 (0.59, 1.27) 0.89(0.57,1.39)

77

6 Discussion

A cross-sectional survey was used to investigate restorative material choice and rubber dam use

by pediatric dentists in Canada and the US through a variety of scenarios involving both primary

and permanent posterior teeth. Restorative dentistry comprises a large portion of pediatric dental

practice and restorative material choice should reflect evidence-based research. The specific

scenarios were not represented with radiographs or clinical photos in order to minimize

interpretation discrepancies (Mileman & van der Weele, 1996; Espelid & Tveit, 2001; Ohiomoba

& Nelson, 2013). Thus, to ascertain the practitioners’ philosophy of practice, ideal scenarios with

a cooperative child, good oral hygiene, and lack of time constraints were provided.

6.1 Choice of Material

Compared to the previous North American literature on restorative material use, this study

showed an increased use of composite resin for primary and permanent teeth. Composite was

chosen by half (51.3%) of the respondents for primary Class II restorations, followed by

amalgam (17.3%), and SSC (10.8%) while in a 2004 survey, amalgam was chosen the most often

(57%) in California (Pair et al., 2004). In addition, for permanent restorations, composite was

overwhelmingly chosen in this study for Class I, II, and V restorations at 83.4%, 74.3%, and

79.0%, respectively. These results are similar to surveys done in Florida, Belgium, Finland,

Norway, Croatia, Sweden, and Australia where the restorative material of choice is composite

resin (Van Meerbeek et al., 1991; Espelid et al., 2001; Forss & Widstrom, 2001; Guelmann &

Mjor, 2002; Tran & Messer, 2003; Vidnes-Kopperud et al., 2009; Baraba et al., 2010). However,

these studies may be misleading as many European countries have mercury

reduction/elimination programs so amalgam is unable to be used for environmental reasons not

due to the dentists’ preference. In Canada, amalgam was chosen over composite (OR 0.44; CI

0.28-0.69) and white restorations (OR 0.73; CI 0.65-0.82). Further research is necessary to

determine the cause of this finding but potentially, the push for esthetic restorations is not as

prominent in Canada. In 2011, the International Society of Aesthetic Plastic Surgery assessed the

number of non-surgical and surgical esthetic procedures completed; the United States ranked

number 1 while Canada ranked number 15 (ISAPS, 2011). This trend may also be seen for

78

esthetic dental restorations. In 1975 and 1984, the American Academy of Esthetic Dentistry

(Chicago) and American Academy of Cosmetic Dentistry (Madison, Wisconsin) were

established (Christensen, 2011; AACD, 2014). In Canada, the establishment of similar

associations has been more recent with the founding of the Canadian Academy of Cosmetic

Dentistry and the Canadian Academy for Esthetic Dentistry; however, information about these

academies is limited due to their websites being under construction. However, at the 2008 Pacific

Dental Conference in Vancouver, Canada, the Canadian Academy for Esthetic Dentistry

sponsored and organized two days of lectures (CAED, 2008; OHG, 2008). The later

establishment of these organizations may show that Canada follows trends set by the United

States of America.

This is a unique study as it evaluates the restorative material choice for three different

populations: healthy, medically compromised (MC), and developmentally delayed (DD). There

is limited information on restorative material choice for children with special health care needs;

this investigation can act as a baseline for future studies. In this study, MC individuals followed

the trend for healthy individuals; Class I, II, and V restorations in primary teeth were treated

mainly by composite (41.6%, 36.6%, and 36.3%, respectively), then stainless steel crowns

(26.6%, 28.6%, and 32.9%, respectively), followed by amalgam (13.4%, 16.6%, and 9.2%,

respectively). For permanent teeth, composite resin was chosen the most often for all

restorations. One could speculate that the caregivers of a MC individual may want a material

with a lower perceived toxicity; thus, the use of composite resin may be requested. In a

retrospective cross-sectional clinical study performed at a dental school in Seoul, Korea, no

difference in longevity of amalgam and composite restorations was found if the patient had a

systemic disease (Rho et al., 2013). However, this study has two major differences from our

population: the patients’ age ranged from 10-78 and the systemic diseases included were, but not

limited to, hypertension, diabetes, and hepatitis. More research is necessary to ascertain why the

trends for MC individuals follow the healthy cohort instead of the DD group. Potentially, dentists

group MC and healthy individuals together due to similar cognitive capability while DD

individuals may be perceived to have poorer behaviour and communication skills. For DD

individuals, SSC was chosen the most often for primary Class I, II, and V restorations while

amalgam and composite were chosen at similar lower frequencies. Epidemiologically, the DD

79

population has a higher caries risk (Chi et al., 2013). SSC may have been chosen due to the

relative ease of restoration especially if the behaviour is difficult and caries risk is high (Charles,

2010; AAPD, 2012). In this study for permanent teeth, amalgam was used the most often for

Class I and II restorations but composite was used slightly more for Class V restorations (35.5%

for composite compared to 34.1% for amalgam); thus, showing the value of longevity and

minimal technique sensitivity in this population. Interestingly, RMGI was used by a small

percentage of the respondents for restorations in permanent teeth. Although some authors

suggest that glass ionomer should be used the most often in permanent teeth of DD individuals;

glass ionomers’ major limitations of poor wear characteristics, poor compressive strength, and

brittleness, make it a sub-par material especially in areas with high occlusal loading (Mjor, 1997;

Berg, 1998; Gryst & Mount, 1999; Fuks et al., 2000; Ersin et al., 2006).

This study not only evaluated the preferred choice of material but also the reasons for choosing

each material. Disheartening findings include that a greater number of respondents believe using

composite is more evidence-based (76.9%) than amalgam (61.1%) and that both materials have

good mechanical properties. The current literature supports that amalgam has greater longevity

than composite in both the primary and permanent posterior dentition (Levering & Messer, 1988;

Berg, 1998; Bernardo et al., 2007; Kovarik, 2009; Rho et al., 2013; Rasines Alcaraz et al., 2014).

With the advances in composite bonding and operator experience, a trend of decreasing failure

rates has been seen; however, despite the improvements, the longevity is still shorter than

amalgam (Hickel et al., 2005; Gjorgievska et al., 2008; Opdam et al., 2010). In a retrospective

study by Rho et al. (2013), the median survival time of a Class I amalgam was 10 years (range

7.9-15.5) while composite was 3.3 years (range 2.5-10.5). In the ten year old age group, the

survival time for amalgam was 10 years while for composite it was 1.2 years, showing that for

younger children, amalgam should be the preferred restoration. Due to the higher failure rate of

composite resin, it is suggested that they require more frequent follow up for early detection of

failure (Rho et al., 2013). In Finland, the perception of dentists regarding restoration longevity

was evaluated by Palotie and Vehkalahti (2009). In this study, the mean estimate for the

longevity of amalgam (18.7 years; SD 7.3; 95% CI 18.0-19.5) was two times higher than

composite (9.0 years; SD 3.6; 95% CI 8.6-9.3). It seems that although dentists recognize that

80

amalgam has greater longevity, other factors such as government regulations and esthetics drive

them to choose composite (Nyheter, 2007).

In both this study and previous publications, important reasons for choosing composite include

the caregivers’ insistence for a tooth coloured restoration (Guelmann & Mjor, 2002; Burke et al.,

2003; Espelid et al., 2006). These restorations may be favoured not only for esthetics but also the

perception that they have a positive psychological effect, thereby, increasing self-esteem (Davis,

Ashworth, & Spriggs, 1998). In Florida, the restorative material preference among children was

evaluated; among composite, amalgam, and stainless steel crowns, composite was the first

choice for 44% of 5-8 year olds and 53% of 9-12 year olds (Fishman, 2006). A study evaluating

patients, dental assistants, and dentists’ preference about restorative material found that patients

and dental assistants were willing to trade the longevity of a restoration for an improved

appearance (Espelid et al., 2006).

The scientific factors chosen most often for composite include that it allows for a conservative

preparation (91.2%), is less allergenic (48.1%), and has a lower toxicity than other materials

(35.9%). Currently, the debate about toxicity in restorative materials revolves around mercury in

amalgam; however, the leaching of BPA derivatives in composite resin should also be a concern

(Fleisch et al., 2010). Pure BPA is not a component of composite resin but it has been detected in

saliva for up to three hours after placement (Fung et al., 2000; Sasaki et al., 2005; Fleisch et al.,

2010). BPA and its’ derivatives are not benign; multiple animal and in-vitro studies have shown

the detrimental effects of BPA such as fibroblast death caused by Bis-GMA (Fleisch et al.,

2010). However, there is controversy as to whether these studies are relevant to humans. In direct

human epidemiological studies, there has been an association between BPA and low follicle

stimulating hormone levels in occupationally exposed women, polycystic ovarian syndrome, and

high testosterone levels in both men and women (Fleisch et al., 2010). In June 2009, the “high

uncertainty in the data” prompted a precautionary action by banning the use of BPA in baby

bottles in Canada (Agency, 2010). Amalgam has been investigated thoroughly secondary to

concerns about toxicity; currently, no permanent neurologic, renal, or immune deficiencies have

been found in children (Khordi-Mood et al., 2001; Kingman et al., 2005; DeRouen et al., 2006;

Bellinger et al., 2007; Shenker et al., 2008). In regards to allergenicity, there have been adverse

reactions to composite restorations that include contact dermatitis, intraoral ulcers, swollen lips,

81

and respiratory reactions such as asthma (Kanerva et al., 2000; Tillberg et al., 2009). Although

these reactions were primarily intraoral and half disappeared within a week, they still show that

composite resins have toxicity and may cause other adverse outcomes.

In addition to the potential toxicity of the materials, other factors that influence the respondents’

choice for material include the busyness of the practice. In this study, if the respondents

performed fewer recalls per day, they were more likely to choose amalgam than SSC and

composite. In contrast, Makhija et al. (2011) reported that amalgam was chosen over composite

if the dentist was ‘too busy to treat all patients’ and ‘provided care to all patients but

overburdened’. When the dentist was ‘not busy enough’, the practitioner choose composite over

amalgam; the luxury of time allows for proper placement of composite since it is technique

sensitive (Sjogren & Halling, 2002; Beazoglou et al., 2007; Makhija et al., 2011). Furthermore,

in some regions there is the benefit of increased monetary compensation. The relative re-

imbursement of composite resin may be twice as high as glass ionomer or amalgam (Sjogren &

Halling, 2002). Beazoglou et al. (2007) created an economic model to predict dental

expenditures if an amalgam ban was instituted in the US. The ban would increase the average

price of restorations by $52 each, causing the total expenditures to increase by $3.5 billion

dollars. The economic impact of switching to composite restorations could potentially decrease

access to care for low socioeconomic patients who have a higher dental caries risk and lower

relative disposable income.

The caries risk of the patient should influence the choice of restorative material; the restoration

should be easy to maintain and long lasting with a low initial and replacement cost (Goldberg et

al., 1981; AAPD, 2013). For patients with poor oral hygiene, the majority of the participants

chose SSC (90.6%), and amalgam (45.9%) as the most appropriate material. When assessing the

tooth factors that affect restorations, SSC and amalgam were chosen the most often for

subgingival preparation margins (85.5% and 44%, respectively), gross caries requiring a large

preparation (95.1% and 21.9%, respectively), and an inability to obtain proper isolation (73.7%

and 54.2%, respectively). The response from the participants is appropriate as composite

restorations require moisture control to achieve adhesion which subsequently affects the

retention and longevity of the restoration (Braga et al., 2005; Shenoy, 2008). With a higher caries

risk, restorations with a greater longevity are recommended.

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In terms of scientific factors, SSCs had the most favourable response including having scientific

support (92.3%), good mechanical properties (81.4%), fewer steps to restore (66.1%), lower

toxicity than other materials (79.6%), and being historically safe and reliable (89.4%). SSCs

have been shown to be more successful over time than multi-surface direct restorations and

following pulp treatment, so the perception by the respondents is supported by the evidence

(Braff, 1975; Dawson et al., 1981; Holland et al., 1986; Papathanasiou et al., 1994; Randall et al.,

2000; AAPD, 2012).

In this study, the choice of amalgam over tooth coloured restorations was significant for

individuals with an MSc/PhD in comparison to a diploma. With a more rigorous educational

program, one would expect that critical analysis of the literature and adherence to evidence-

based dentistry practices would be more valued. For the option of which material was primarily

taught in school, amalgam and composite were reported to be similar. Guelmann, Mjor, and

Jerrell (2001) evaluated the curriculum of 63 undergraduate dental schools across Canada and

the US; they reported that the majority of programs taught the use of amalgam as the preferred

material for primary molar Class I and II restorations (63%). However, it was noted that hybrid

composites and compomers were gaining popularity. In 2005, a Canadian survey of

undergraduate dental schools also rerported an emphasis on amalgam restorations (McComb,

2005). These dental schools agreed that poor oral hygiene, high risk of caries, gingival margin on

root structure, inability to place rubber dam, and cavity size greater than half to two-thirds of the

intercuspal width are contraindications for composite resin. According to Lynch, Frazier,

McConnell, Blum, and Wilson (2011), “dental education [of posterior composite resins] in the

United States and Canada lags that in the United Kingdom and Ireland, as well as that in other

parts of the world”. In 73% of schools, amalgam placement is taught first and the average

amount of preclinical curriculum time was greater for amalgam than for composite resin;

however, the difference is minimal (40% of preclinical time for amalgam [range, 5-80%] and

37% for composite [range 10-80%]). Recently, restorative material undergraduate curriculum has

been changing; this may be due to the belief that “dental schools [are] out of touch with the

needs of recent graduates in terms of acquiring the skills needed for a key aspect of dental

practice” (Lynch et al., 2011). In US, Canadian, UK, and Irish dental schools, between 1997 to

2005, students’ experience with composite resin increased by almost 200% and the ratio of

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composite resin to amalgam was found to be as high as 2:1 (Lynch, McConnell, & Wilson,

2006a, 2006b; Lynch, 2007). By increasing the educational time devoted to composite resin in

response to the trend in private practice, the lack of proper education regarding the longevity of

materials and indications for placement may graduate new dentists who do not understand the

material science of amalgam and composite. The studies reported above attempt to justify the

placement of composite restorations based upon the “principles of minimally invasive dentistry”

and “the best interests of patients”; however, one could argue that the best treatment for a patient

is a restoration which has greater longevity and antibacterial properties (Lynch et al., 2011). In

this study, glass ionomer and RMGI usage for Class II restorations in primary molars was lower

than reported in previous studies (Guelmann & Mjor, 2002; Forss & Widstrom, 2003; Pair et al.,

2004; Vidnes-Kopperud et al., 2009). This could be due to the significantly inferior clinical

performance of these materials in comparison to amalgam and composite (Qvist et al., 1997;

Forss & Widstrom, 2001; Mjor et al., 2002; Rutar et al., 2002). Another factor could be more

marketing for esthetic restorations including composite resin. With fluoride releasing materials,

the balance between marginal integrity and the therapeutic value of fluoride must be considered

(Burke, Wilson, Cheung, & Mjor, 2001). In this study, only 8.9% of the respondents felt that

fluoride release is ‘very important’ for choosing a restoration while 27.9% reported that it ‘was

not important at all’; this shows that although fluoride release could be beneficial, it is not a

prominent factor.

6.2 Rubber Dam Isolation

In this study, the overall usage of rubber dam isolation was 89.1% with around three quarters

stating that they use it ‘all the time’. This is similar to the 83% reported rubber dam usage among

a selected population of US pediatric dentists (Slawinski & Wilson, 2010). The benefit of this

study is that the sample size is larger and it was distributed across Canada and the US, thus

representing a larger population. In the literature, there is a wide variation for rubber dam usage

(Jones, 1999; Burke et al., 2003; Soldani & Foley, 2007; Hill & Rubel, 2008; Gilbert et al., 2010;

Slawinski & Wilson, 2010). In North American studies, there has been a trend for low usage of

the rubber dam in the general dentist population. A 2008 survey of American general dentists

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showed that rubber dams are used by 61% for posterior composite resins and 47% for posterior

amalgam restorations (Hill & Rubel, 2008). In England, a 2001 survey of general dentists

reported that 53% never use rubber dam isolation for restoring posterior composites (Burke et al.,

2003). In contrast, a survey of UK pediatric dentists reported that rubber dam isolation was used

all the time in 46% of non-sedation cases and most often with composite resin restorations

(Soldani & Foley, 2007). As Lynch and McConnell (2007) stated “it seems paradoxical that a

technique that is advocated as promoting and supporting good clinical practice is often ignored in

routine dentistry”.

Rubber dam isolation is recommended to be used for all restorations due to the benefits including

but not limited to: increased longevity of restorations, decreased environmental microbial

contamination from salivary aerosol, improved access and visibility of the operating field,

moisture control, facilitation of treatment in patients with a pronounced gag reflex, aid in

behaviour management, and protection from aspiration (Cochran et al., 1989; Christensen, 2001;

Lynch & McConnell, 2007; Soldani & Foley, 2007). The vast majority of respondents in this

study use rubber dam isolation in both dentitions; however, it was interesting that the lowest

usage in the primary dentition was with composite resin (82.2%) which differs from previous

studies (Jones & Reid, 1988; Knight et al., 1993; Gilbert et al., 2010). Given that composite resin

requires a dry environment, one would expect that rubber dam isolation would be used more

(Fleisch et al., 2010; Zimmerli et al., 2010).

In this study, rubber dam isolation was significantly associated with those who have MSc or PhD

training and those who primarily practice in academic or hospital based setting. In these settings,

the acquisition of skills for critical evaluation of the dental literature and the emphasis on

evidence-based dental practice could be the reason for increased use (Randall, Vrijhoef, &

Wilson, 2002). In this study, practitioners who accept government funding use rubber dam

isolation more than those who do not accept funding. Potentially, the practitioner may want to

use every method possible to prevent failure of the restoration due to a lower reimbursement for

the initial restoration and limited coverage for replacement restorations. Further investigation is

necessary to support this hypothesis.

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The main reason that the respondents do not use rubber dam isolation is a perceived decreased

trauma to the patient. In other studies, ‘trauma’ was defined as fear of suffocation, patient fear,

and potential for painful stimulus (Slawinski & Wilson, 2010; Kapitan, Sustova, Ivancakova, &

Suchanek, 2014). Slawinski and Wilson (2010) noted that these variables may be due to

“personal experience of the patients rather than those of the practitioner”, thus, creating

reluctance for the practitioner to use the rubber dam. In Scotland in a children’s dental clinic,

rubber dam application was accepted by up to 79% and preferred by 30% of children (Jones &

Reid, 1988). If the application of the rubber dam is uncomfortable, the practitioner can address

the complaint by using topical or local anesthetic in conjunction with other behaviour

management techniques.

This study also found that if a practitioner is busier, they were less likely to use rubber dam

isolation. A study by Heise (1971) found that the average application time for rubber dam

placement in children and adults is 148 seconds. Another study evaluated three different rubber

dam systems on a dental simulator with 6 different scenarios (single vs multiple teeth isolation in

different locations) (Kapitan et al., 2014). For single tooth isolation, the median time for rubber

dam preparation was 31 seconds, placement was 51 seconds, and removal was 12 seconds. For a

group of teeth, the preparation and placement time almost doubled. Although the time required

for placement on a patient instead of a simulator will be increased, with proper technique and

good behaviour management, the time needed is minimal in comparison to treatment time

(Kapitan et al., 2014). In addition, some suggest that using a rubber dam may decrease procedure

time due to lack of expectoration and talking (Christensen, 2001; Slawinski & Wilson, 2010).

A speculation for the lack of use is that rubber dam placement and indications for use was not

properly taught in dental school. However, surveys of dental students showed that although

usage in school is high, more than half predicted that their use of rubber dam isolation would

decrease after graduation (Hill & Rubel, 2008; Mala, Lynch, Burke, & Dummer, 2009). When

assessing the attitudes of fourth year dental students, only half agreed that ‘posterior restorations

can be placed more easily once the rubber dam has been applied’ (53%) and that ‘restorations

placed under rubber dam have a greater longevity than those placed without’ (60%) (Mala et al.,

2009). Interestingly, when general dentists were asked similar questions there was a much lower

level of agreement: only 39% agreed that ‘posterior restorations can be placed more quickly

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when rubber dam is used’, 32% agreed that ‘a higher clinical standard is achievable when

restorations are placed under rubber dam’, and 43% agreed that ‘restorations placed under rubber

dam have a higher longevity than those placed without rubber dam’ (Lynch & McConnell,

2007). The attitude that rubber dam is difficult to place was similar in students (53%) and

general practitioners (57%) (Lynch & McConnell, 2007; Mala et al., 2009). One would assume

that the change in perception in rubber dam usage could be that the dentists have ‘not been

taught or have forgotten how to use the rubber dam’ but only 32% of general dentists agreed

with this statement. This shows that although the rubber dam is taught in school, practitioners do

not value its ability to isolate for the longevity of the restoration. Even though 83% of pediatric

dentists use rubber dam isolation, over half of the pediatric dentistry residency program directors

and private practice pediatric dentists felt that rubber dam principles should be emphasized more

in training (Slawinski & Wilson, 2010). In this study, all Canadian respondents (100%) use

rubber dam isolation in comparison to most American respondents (87.7%). This may be due to

the emphasis of the rubber dam in teaching; however, more studies are necessary.

6.3 Preference of Role in Decision-Making

For health care professionals, making decisions is one of the most challenging yet important

activities. Traditionally, health care professionals, including dentists, made decisions through the

combination of learned material, individual perception through experience, dental practice

traditions, and sometimes, research (McCreery & Truelove, 1991; Bader & Shugars, 1995;

Charles, Gafni, & Whelan, 1999; Richards, 1999). Decision-making was considered to be an

“inherent part of the skills of dentists, acquired through experience, but not taught easily”

(McCreery & Truelove, 1991). Now, it has moved from a more patriarchal approach to shared

decision-making which aims to help patients have a more active role to achieve the “ultimate

goal of patient-centered care” (Kaplan, Greenfield, Gandek, Rogers, & Ware, 1996; Charles et

al., 1999; Richards, 1999; Gravel, Legare, & Graham, 2006). Although, variability in the

dentists’ preference for material can be expected which reflects the “best clinical judgment” or

“art of dentistry”, it is imperative to establish a context where patients’ views about treatment

options are valued (Gravel et al., 2006; Azarpazhooh, Dao, Figueiredo, Krahn, & Friedman,

87

2013; Mills, Frost, Cooper, Moles, & Kay, 2014). Shared decision-making involves introducing

evidence-based treatment options, discussing the benefits and risks of each option, properly

eliciting patients’ preference, and sharing treatment recommendations (Gravel et al., 2006;

Elwyn et al., 2012; Scarbecz, 2012; Mills et al., 2014). To elicit the preferred role in decision

making, the Controlled Preferences Scale (CPS) was originally designed for oncology patients

but has been successfully transferred to other specialties such as endocrinology, internal

medicine, general surgery, and recently, dentistry; these studies have shown that, from the

patients’ perspective, decision-making is multifactorial and difficult (Degner et al., 1997; Kiesler

& Auerbach, 2006; Say, Murtagh, & Thomson, 2006; Wilkinson, Khanji, Cotter, Dunne, &

O'Keeffe, 2008; Singh et al., 2010; Zhang et al., 2011; Azarpazhooh et al., 2014). In order to

create a model to aid with decision-making for restorative materials in children, we chose to use

the CPS tool for dentists instead of patients (Degner et al., 1997). By eliciting the dentists’

preferred role, we may be able to reconcile any discrepancy in preferred participation between

dentists and patients. In this study, over half of the participants preferred to have an active role

(58.3%) especially females and those who seldom or never have pressure from caregivers as

compared to those who sometimes have pressure. If trust is established, patients’ often prefer a

passive or collaborative role, thus complementing the active role preferred by dentists (Chapple,

Shah, Caress, & Kay, 2003). However, Chapple et al. (2003) found that patients, in private

practice and hospital based settings, who have a lack of trust in their dentist are those who least

prefer the passive role. This was supported by comments such as ‘I think he can make the wrong

decision’ and ‘I wouldn’t like to leave everything up to him, he could mess everything up’. An

interesting finding was that the majority of the patients in both sites perceived that they had

attained a passive role in decisions due to time constraints for discussion and lack of knowledge.

It has been suggested that time available for discussion will allow for more effective

communication which may increase the patients’ trust and thereby, allow for more shared

decision-making (Chapple et al., 2003; Gravel et al., 2006; Scarbecz, 2012).

The preference for a passive role for patients is similar across the health care field; it is

consistent with a provider-recipient/paternalistic model instead of the collaborative role which

has been promoted in recent literature and healthcare policy (Charles et al., 1999; Richards,

1999; Chapple et al., 2003). In this study, a passive role was preferred by pediatric dentists who

88

work in a hospital-based or university-based setting compared to a combined setting. For

patients, a ‘collaborative-active’ preference order was found in the hospital-based setting which

corresponds to the preferred passive role by dentists that were found in this study (Chapple et al.,

2003).

In addition to trust and communication, other factors that the respondents noted to be significant

in treatment planning include financial issues such as out of pocket expense and insurance

coverage. With an increase in insurance, the utilization of dental services for children has

increased in the US (Feinberg, Swartz, Zaslavsky, Gardner, & Walker, 2002; Kenney, Marton,

Klein, Pelletier, & Talbert, 2011; Wall, Vujicic, & Nasseh, 2012; Vujicic & Nasseh, 2014).

Depending on insurance coverage, patients and caregivers may opt for less expensive

restorations such as amalgam in comparison to composite (Beazoglou et al., 2007). If amalgam

restorations were to be phased out, it could cause more issues with access to care for lower

income patients.

In this study, we evaluated how often the respondents are questioned about the toxicity of

amalgam and composite from caregivers. About half of the pediatric dentist respondents

‘seldom’ have patients or caregivers with concerns about the type of restorative material that is

used. In response to pressure, we chose the ‘right answer’ to be either continuing to convince the

caregiver about the dentists’ preferred restoration or to refer the patient to a different practitioner.

With the assumption that the dentist has chosen the ideal restoration after thoroughly evaluating

the literature, these options were chosen to maintain the integrity of the dentists’ decision. It was

found that the respondents who were pressured “all/most of the time” chose the right answer less

frequently than those who were pressured ‘sometimes’ or ‘never’. Potentially, the frequency of

conflict causes the respondent to feel like he or she is fighting a losing battle; thus, shared

decision-making is not upheld. When asked about mercury toxicity, the vast majority discussed

the evidence of low mercury release from amalgam to inform the caregivers; this is an

appropriate evidence-based method of involving the caregiver in shared decision-making.

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6.4 Survey Tool and Demographics

When evaluating survey demographics, an assumption is that both responders and non-

responders are the same. The demographics of our sample varied in terms of length of time in

practice from the previous North American studies about restorative material choice. The sample

had a fairly well spread range (Table 5.1), while older studies were more skewed to greater than

15 years (Pair et al., 2004). In comparison to recent surveys done on the AAPD population, the

demographics were similar with about an equal number of males and females, a fairly uniform

spread of years of practice, and the majority in private practice with combined (hospital and

university) postgraduate training (Dunlop, Sanders, Jones, Walker, & Caldwell, 2013; Juntgen et

al., 2013; Sivaraman, Hassan, & Pearson, 2013). From a statistical perspective, it is appropriate

to consider the respondents in this study as representative of the practicing pediatric dental

population.

Using a web-based survey, this study was able to access the population of active practicing

pediatric dentists in Canada and the United States in a cost effective, efficient manner (Ahern,

2005). A pilot study was completed in order to minimize equipment difficulty, network

incompatibility, and survey malfunction due to complex programming; thus, potentially

increasing the number of fully completed surveys.

In order to generalize the data obtained from a survey to a population, a high response rate is

essential; above 80% is the optimal response rate (Evans, 1991; Wyatt, 2000; Parashos et al.,

2005). Over ten years ago, web-based surveys with no follow-up reminders were expected to

have a 25-30% response rate (Kittleson, 1997). Since the popularity of web-based surveys has

increased, survey fatigue may make it difficult to achieve this high level response rate (Wyatt,

2000). When individuals reach a saturation point of e-mails and surveys received, one would

expect a decreased response rate (Kittleson, 1997; Cook, Heath, & Thompson, 2000). In this

study, the response rate of 19.3% is comparable to other online surveys using the practicing

members of the American Academy of Pediatric Dentistry (Dunlop et al., 2013; Juntgen et al.,

2013; Sivaraman et al., 2013). Although the response rate is low, the calculated sample size was

355 so the response of 762 participants is still adequate and representative of the sample.

90

Responder bias occurs with web-based surveys as the “more active and concerned segments of

the dental community” may respond more often (Parashos et al., 2005). According to Parashos et

al. (2005), some reasons for non-response can be lack of time, lack of interest, part-time work,

being away from the office, and no specific reason. This survey assessed a large amount of

information; its length may have decreased the response rate. Access to a computer can limit the

number of responders; however, a 2006 assessment of Canadian dental practices showed that

90% of the respondents have access to a computer in their primary practice (Flores-Mir, Palmer,

Northcott, Huston, & Major, 2006). Among the population of pediatric dentists, the lack of

computer or internet access is negligible.

When assessing the validity of the study, Table 5.5 shows that the survey participants understood

the wording and format of this study. For the response ‘allows for fluoride release’, 0% chose

amalgam and 0.4% chose SSC which is an appropriate response as these materials do not release

fluoride (Randall et al., 2000). In addition, for the esthetically pleasing factor, 0.4% chose

amalgam and 0.9% chose SSC. If the survey was difficult to understand, these numbers may

have conflicted with the material; this verifies that the respondents did not misunderstand the

questions due to the format of the survey (Randall et al., 2000; Fuks, 2002).

6.5 Limitations

The limitations of this study are mainly from its methodology as a web-based survey. Although

this is an appropriate way to distribute the tool to a large number of people, the lack of response

and the similar response rates to other on-line surveys from this population show that this may

not be the best approach. Another issue was a coding error where the question about composite

toxicity did not appear on the survey. The response to this question would have been helpful to

compare the perception of toxicity between composite and amalgam. Another limitation is the

length of the survey. Multiple recipients refused to complete the survey secondary to its length

and the lack of personal time. A more efficient way to use this tool would be sending multiple

shorter surveys or using fewer scenarios.

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6.6 Future Directions

The future directions of this research project involve decision-making. Regardless of the

dentists’ preference in choice of material, the decision must be taken by the patient and his/her

caregiver. In order to make a well-informed decision, the information provided by the dentist as

well as the opportunity to engage in discussion is imperative. The preferred choice of material

for the caregivers as well as the child could be explored to see if and where there is a gap in

knowledge and how to address those inadequacies. In addition, this study assessed only the

preferences of the respondents. In order to assess what occurs in actual practice, private and

public insurance claims could also be assessed.

7 Conclusions

With the limitations of this study, the responses of the surveyed pediatric dentists show that:

Composite resin is the most preferred restoration for primary Class I, II and V restorations in

primary and permanent teeth in healthy and medically compromised individuals

Stainless steel crown is the preferred restoration for Class I, II, and V primary tooth posterior

restorations in the developmentally delayed population. Amalgam is chosen slightly more often

than composite in the permanent dentition

Pediatric dentists’ perception regarding the poor longevity and mechanical properties of

composite has changed

Rubber dam usage is valued as the majority of pediatric dentists choose to use it for all materials

Pediatric dentists generally prefer to have an active role in shared decision-making except in a

hospital-based or university based setting in comparison to private practice.

92

References

Primary Sources

Secondary Sources

Uncategorized References

AACD. (2014). Welcome to the American Academy of Cosmetic Dentistry. American Academy

of Cosmetic Dentistry Retrieved from http://www.aacd.com/about

AAPD. (2012, 2012). Guideline on Pediatric Restorative Dentistry. Retrieved December 30,

2013, from http://www.aapd.org/media/Policies_Guidelines/G_Restorative.pdf

AAPD. (2013). Guideline on Caries-risk Assessment and Management for Infants, Children, and

Adolescents. Clinical Guidelines Reference Manual, 35(6).

Aboush, Y. E., & Torabzadeh, H. (1998). Fluoride release from tooth-colored restorative

materials: a 12-month report. J Can Dent Assoc, 64(8), 561-564, 568.

ADA. (2005). ADA Guidelines on Amalgam Accumulations in Dental Office Plumbing [Press

release]. Retrieved from

http://www.ada.org/sections/professionalResources/pdfs/amalgam_plumbing_guidelines.

pdf

ADA. (October 2007). Best Management Practices for Amalgam Waste. American Dental

Association Retrieved from

http://www.ada.org/sections/professionalResources/pdfs/topics_amalgamwaste_brochure.

pdf.

Affairs, A. C. o. S. (1998). Dental amalgam: update on safety concern. J Am Dent Assoc(129),

484-503.

Affairs, A. C. o. S. (2010). Literature Review: Dental Amalgam Fillings and Health Effects.

Retrieved from

http://www.ada.org/sections/professionalResources/pdfs/amalgam_literature_review_100

9.pdf.

Agency, U. S. E. P. (2010). Bisphenol A - Action Plan. Retrieved December 30, 2013

Ahern, N. R. (2005). Using the Internet to conduct research. Nurse Res, 13(2), 55-70. doi:

10.7748/nr2005.10.13.2.55.c5968

AlNegrish, A. (2001). Reasons for placement and replacement of amalgam restorations in

Jordan. Int Dent J, 51(2), 109-115.

93

AlNegrish, A. (2002). Composite resin restorations: a cross-sectional seurvey of placement and

replacement in Jordan. Int Dent J, 52(6), 461-468.

Aminzadeh, K. K., & Etminan, M. (2007). Dental amalgam and multiple sclerosis: a systematic

review and meta-analysis. J Public Health Dent, 67(1), 64-66.

Asmussen, E. (1982). Factors affecting the quantity of remaining double bonds in restorative

resin polymers. Scand J Dent Res, 90(6), 490-496.

Attin, T., Buchalla, W., Kielbassa, A. M., & Helwig, E. (1995). Curing shrinkage and volumetric

changes of resin-modified glass ionomer restorative materials. Dent Mater, 11(6), 359-

362.

Attin, T., Vataschki, M., & Hellwig, E. (1996). Properties of resin-modified glass-ionomer

restorative materials and two polyacid-modified resin composite materials. Quintessence

Int, 27(3), 203-209.

Australian Research Center for Population Oral Health, T. U. o. A., South Australia. (2004).

Changes in South Australian children's caries experience: Is caries re-surfacing? . Aust

Dent J, 49(2), 98-100.

Azarpazhooh, A., Dao, T., Figueiredo, R., Krahn, M., & Friedman, S. (2013). A survey of

dentists' preferences for the treatment of teeth with apical periodontitis. J Endod, 39(10),

1226-1233. doi: 10.1016/j.joen.2013.06.023

Azarpazhooh, A., Dao, T., Ungar, W. J., Chaudry, F., Figueiredo, R., Krahn, M., & Friedman, S.

(2014). Clinical decision making for a tooth with apical periodontitis: the patients'

preferred level of participation. J Endod, 40(6), 784-789. doi: 10.1016/j.joen.2014.01.045

Azarpazhooh, A., & Main, P. A. (2008). Is there a risk of harm or toxicity in the placement of pit

and fissure sealant materials? A systematic review. J Can Dent Assoc, 74(2), 179-183.

Bader, J. D., & Shugars, D. A. (1995). Variation, treatment outcomes, and practice guidelines in

dental practice. J Dent Educ, 59(1), 61-95.

Bains, V. K., Loomba, K., Loomba, A., & Bains, R. (2008). Mercury sensitisation: review,

relevance and a clinical report. Br Dent J, 205(7), 373-378. doi: 10.1038/sj.bdj.2008.843

Baraba, A., Domejean-Orliaguet, S., Espelid, I., Tveit, A. B., & Miletic, I. (2010). Survey of

Croatian dentists' restorative treatment decisions on approximal caries lesions. Croat Med

J, 51(6), 509-514.

Baratieri, L. N., & Ritter, A. V. (2001). Four-year clinical evaluation of posterior resin-based

composite restorations placed using the total-etch technique. J Esthet Restor Dent, 13(1),

50-57.

94

Barregard, L., Trachtenberg, F., & McKinlay, S. (2008). Renal effects of dental amalgam in

children: the New England children's amalgam trial. Environ Health Perspect, 116(3),

394-399. doi: 10.1289/ehp.10504

Bates, M. N., Fawcett, J., Garrett, N., Cutress, T., & Kjellstrom, T. (2004). Health effects of

dental amalgam exposure: a retrospective cohort study. Int J Epidemiol, 33(4), 894-902.

doi: 10.1093/ije/dyh164

Beazoglou, T., Eklund, S., Heffley, D., Meiers, J., Brown, L. J., & Bailit, H. (2007). Economic

impact of regulating the use of amalgam restorations. Public Health Rep, 122(5), 657-

663.

Bellinger, D. C., Daniel, D., Trachtenberg, F., Tavares, M., & McKinlay, S. (2007). Dental

amalgam restorations and children's neuropsychological function: the New England

Children's Amalgam Trial. Environ Health Perspect, 115(3), 440-446. doi:

10.1289/ehp.9497

Bellinger, D. C., Trachtenberg, F., Barregard, L., Tavares, M., Cernichiari, E., Daniel, D., &

McKinlay, S. (2006). Neuropsychological and renal effects of dental amalgam in

children: a randomized clinical trial. JAMA, 295(15), 1775-1783. doi:

10.1001/jama.295.15.1775

Bellinger, D. C., Trachtenberg, F., Zhang, A., Tavares, M., Daniel, D., & McKinlay, S. (2008).

Dental amalgam and psychosocial status: the New England Children's Amalgam Trial. J

Dent Res, 87(5), 470-474.

Ben-Amar, A., Cardash, H. S., & Judes, H. (1995). The sealing of the tooth/amalgam interface

by corrosion products. J Oral Rehabil, 22(2), 101-104.

Berdouses, E., Vaidyanathan, T. K., Dastane, A., Weisel, C., Houpt, M., & Shey, Z. (1995).

Mercury release from dental amalgams: an in vitro study under controlled chewing and

brushing in an artificial mouth. J Dent Res, 74(5), 1185-1193.

Berg, J. H. (1998). The continuum of restorative materials in pediatric dentistry--a review for the

clinician. Pediatr Dent, 20(2), 93-100.

Berglund, A., & Molin, M. (1991). Merucry levels in plasma and urine after removal of amalgam

restorations: the effect of using rubber dams. Dent Mater J, 13(5), 297-304.

Bernardo, M., Luis, H., Martin, M. D., Leroux, B. G., Rue, T., Leitao, J., & DeRouen, T. A.

(2007). Survival and reasons for failure of amalgam versus composite posterior

restorations placed in a randomized clinical trial. J Am Dent Assoc, 138(6), 775-783.

Berry, T. G., Nicholson, J., & Troendle, K. (1994). Almost two centuries with amalgam: where

are we today? J Am Dent Assoc, 125(4), 392-399.

Berthold, M. (2002). Restorative trend data shows shift in use of materials ADA News, 33(1), 10-

11.

95

Bjorkman, L., Lundekvam, B. F., Laegreid, T., Bertelsen, B. I., Morild, I., Lilleng, P., . . .

Vahter, M. (2007). Mercury in human brain, blood, muscle and toenails in relation to

exposure: an autopsy study. Environ Health, 6, 30. doi: 10.1186/1476-069X-6-30

Bowen, R. L. (1963). Properties of a silica-reinforced polymer for dental restorations. J Am Dent

Assoc, 66, 57-64.

Bowen, R. L. (1965). Adhesive Bonding of Various Materials to Hard Tooth Tissues. I. Method

of Determining Bond Strength. J Dent Res, 44, 690-695.

Braff, M. H. (1975). A comparison between stainless steel crowns and multisurface amalgams in

primary molars. ASDC J Dent Child, 42(6), 474-478.

Braga, R. R., Ballester, R. Y., & Ferracane, J. L. (2005). Factors involved in the development of

polymerization shrinkage stress in resin-composites: a systematic review. Dent Mater,

21(10), 962-970. doi: 10.1016/j.dental.2005.04.018

Braga, S. R., Vasconcelos, B. T., Macedo, M. R., Martins, V. R., & Sobral, M. A. (2007).

Reasons for placement and replacement of direct restorative materials in Brazil.

Quintessence Int, 38(4), e189-194.

Braithwaite, D., Emery, J., De Lusignan, S., & Sutton, S. (2003). Using the Internet to conduct

surveys of health professionals: a valid alternative? Fam Pract, 20(5), 545-551.

Brannstrom, M. L., LA.; Astrom, A. (1967). The hydrodynamics of the dental tubule and of pulp

fluid. A discussion of its significance in relation to dentinal sensitivity. Caries Res(1),

310-317.

Brannstrom, M. L., LA; Johnson, G. (1968). Movement of dentinal and pulpal fluid caused by

clinical procedures. J Dent Res(47), 679-682.

Brickhouse, T. H. (2011). Preformed metal crowns may be the most successful restorative

treatment for primary molars. J Evid Based Dent Pract, 11(1), 12-13. doi:

10.1016/j.jebdp.2010.12.002

Burgess, J. O., Barghi, N., Chan, D. C., & Hummert, T. (1993). A comparative study of three

glass ionomer base materials. Am J Dent, 6(3), 137-141.

Burke, F. J., McHugh, S., Hall, A. C., Randall, R. C., Widstrom, E., & Forss, H. (2003).

Amalgam and composite use in UK general dental practice in 2001. Br Dent J, 194(11),

613-618.

Burke, F. J., McHugh, S., Randall, R. C., Meyers, I. A., Pitt, J., & Hall, A. C. (2004). Direct

restorative materials use in Australia in 2002. Aust Dent J, 49(4), 185-191.

Burke, F. J., Wilson, N. H., Cheung, S. W., & Mjor, I. A. (2001). Influence of patient factors on

age of restorations at failure and reasons for their placement and replacement. J Dent,

29(5), 317-324.

96

Busscher, H. J., Rinastiti, M., Siswomihardjo, W., & van der Mei, H. C. (2010). Biofilm

formation on dental restorative and implant materials. J Dent Res, 89(7), 657-665. doi:

10.1177/0022034510368644

CAED. (2008). Canadian Academy for Esthetic Dentistry Retrieved August 16, 2008 from

http://www.oralhealthgroup.com/news/caed-canadian-academy-for-esthetic-

dentistry/1000218957/?type=Print%20Archives

Caldwell, R. (2014a). Trust and Value: The Cause of Disconnect. Ontario Dentist,

January/February 2014, 12.

Caldwell, R. (2014b). Two Serious Concerns. Ontario Dentist, March 2014, 12.

Canada, E. (2002). Memorandum of Understanding: Respecting the Implementation of the

Canada-wide Standard on Mercury for Dental Amalgam Waste Retrieved from

http://www.ec.gc.ca/mercure-mercury/DCEA2675-478B-4078-A1AA-

E47F654F51F7/EC_CDA_MOU.pdf.

Canada, H. (2004). Mercury: Your Health and the Environment. A Resource Tool.

Canada, H. (2007). Human Health Risk. Assessment of Mercury in Fish and Health Benefits of

Fish Consumption. Retrieved from

http://www.elika.net/datos/articulos/Archivo232/HealthCanada_HgPescado07.pdf.

Cantrell, M. A., & Lupinacci, P. (2007). Methodological issues in online data collection. J Adv

Nurs, 60(5), 544-549. doi: 10.1111/j.1365-2648.2007.04448.x

Casamassimo, P. S., Thikkurissy, S., Edelstein, B. L., & Maiorini, E. (2009). Beyond the dmft:

the human and economic cost of early childhood caries. J Am Dent Assoc, 140(6), 650-

657.

CDC. (2013). Oral Health Strategic Plan for 2011-2014. IV. Goals: Focusing the Efforts of the

Oral Health Program.: Center for Disease Control and Prevention Retrieved from

http://www.cdc.gov/OralHealth/strategic_planning/plan4.htm.

Chapple, H., Shah, S., Caress, A. L., & Kay, E. J. (2003). Exploring dental patients' preferred

roles in treatment decision-making - a novel approach. Br Dent J, 194(6), 321-327;

discussion 317. doi: 10.1038/sj.bdj.4809946

Charles, C., Gafni, A., & Whelan, T. (1999). Decision-making in the physician-patient

encounter: revisiting the shared treatment decision-making model. Soc Sci Med, 49(5),

651-661.

Charles, J. M. (2010). Dental care in children with developmental disability, attention deficit

disorder, intellectual disabilities,a nd autism. J Dent Child, 77, 84-91.

97

Chi, D. L., Rossitch, K. C., & Beeles, E. M. (2013). Developmental delays and dental caries in

low-income preschoolers in the USA: a pilot cross-sectional study and preliminary

explanatory model. BMC Oral Health, 13, 53. doi: 10.1186/1472-6831-13-53

CHMS, H. C.-. (2007-2009). Report on the Findings of the Oral Health Component of the

Canadian Health Measures Survey. Minister of Health Retrieved from

http://www.fptdwg.ca/assets/PDF/CHMS/CHMS-E-tech.pdf.

Christensen, G. J. (1996). Restoration of pediatric posterior teeth. J Am Dent Assoc, 127(1), 106-

108.

Christensen, G. J. (1998). Amalgam vs. composite resin: 1998. J Am Dent Assoc, 129(12), 1757-

1759.

Christensen, G. J. (2001). Restorative dentistry for pediatric teeth. State of the art 2001. J Am

Dent Assoc, 132(3), 379-381.

Christensen, G. J. (2011). Dentistry's forced return to its roots. J Am Dent Assoc, 142(12), 1393-

1395.

Chung, K. H., & Greener, E. H. (1990). Correlation between degree of conversion, filler

concentration and mechanical properties of posterior composite resins. J Oral Rehabil,

17(5), 487-494.

CIHI, C. I. f. H. I.-. (2013). Dental Caries Information Sheet.

Clarkson, T. W., & Magos, L. (2006). The toxicology of mercury and its chemical compounds.

Crit Rev Toxicol, 36(8), 609-662. doi: 10.1080/10408440600845619

Cochran, M., Miller, C. H., & Sheldrake, M. A. (1989). The efficacy of the rubber dam as a

barrier to the spread of microorganisms during dental treatment. JADA, 119(July), 143-

144.

Collins, C. J., Bryant, R. W., & Hodge, K. L. (1998). A clinical evaluation of posterior

composite resin restorations: 8-year findings. J Dent, 26(4), 311-317.

Cook, C., Heath, F., & Thompson, R. L. (2000). A meta-analysis of response rates in Web-or

Internet-Based surveys

Educational and Psychological Measurement, 60(6), 821-836.

Cowperthwaite, G. F., Foliy, J. J., & Malloy, M. A. (1981). Polymer Science and Technology

(Vol. 14): C.G. Gebelein and F.F. Klobitz, Plenum Press, New York.

Cox, C. F. E., R.L.; Glasspoole, E. . (1993). Histologic pulp response of a new tricure glass

ionomer. J Dent Res, 72 (Abstr1960): 348.

98

Craelius, W. (1978). Comparative epidemiology of multiple sclerosis and dental caries. J

Epidemiol Community Health, 32(3), 155-165.

Cramer, N. B., Stansbury, J. W., & Bowman, C. N. (2011). Recent advances and developments

in composite dental restorative materials. J Dent Res, 90(4), 402-416. doi:

10.1177/0022034510381263

Crisp, S., Jennings, M. A., & Wilson, A. D. (1978). A study of temperature changes occurring in

setting dental cements. J Oral Rehabil, 5(2), 139-144.

Croll, T. P., Epstein, D. W., & Castaldi, C. R. (2003). Marginal adaptation of stainless steel

crowns. Pediatr Dent, 25(3), 249-252.

Czarnetzki, A. E., S. (1990). Re-dating the Chinese Amalgam-filling of teeth in Europe.

International Journal of Antrhopology, 5(4), 325-332.

Daly, E. (2003). Conducting web based survey research: a lesson in internet designs. American

Journal of Health Behavior, 27(2), 116-124.

Daniels, J. L., Rowland, A. S., Longnecker, M. P., Crawford, P., Golding, J., & Team, A. S.

(2007). Maternal dental history, child's birth outcome and early cognitive development.

Paediatr Perinat Epidemiol, 21(5), 448-457. doi: 10.1111/j.1365-3016.2007.00819.x

Daronch, M., Rueggeberg, F. A., Hall, G., & De Goes, M. F. (2007). Effect of composite

temperature on in vitro intrapulpal temperature rise. Dent Mater, 23(10), 1283-1288. doi:

10.1016/j.dental.2006.11.024

Davis, L. G., Ashworth, P. D., & Spriggs, L. S. (1998). Psychological effects of aesthetic dental

treatment. J Dent, 26(7), 547-554.

Dawson, L. R., Simon, J. F., Jr., & Taylor, P. P. (1981). Use of amalgam and stainless steel

restorations for primary molars. ASDC J Dent Child, 48(6), 420-422.

Degner, L. F., Sloan, J. A., & Venkatesh, P. (1997). The Control Preferences Scale. Can J Nurs

Res, 29(3), 21-43.

Delaviz, Y., Finer, Y., & Santerre, J. P. (2014). Biodegradation of resin composites and

adhesives by oral bacteria and saliva: a rationale for new material designs that consider

the clinical environment and treatment challenges. Dent Mater, 30(1), 16-32. doi:

10.1016/j.dental.2013.08.201

DeRouen, T. A., Martin, M. D., Leroux, B. G., Townes, B. D., Woods, J. S., Leitao, J., . . .

Martins, I. P. (2006). Neurobehavioral effects of dental amalgam in children: a

randomized clinical trial. JAMA, 295(15), 1784-1792. doi: 10.1001/jama.295.15.1784

Dhondt, C. L., De Maeyer, E. A., & Verbeeck, R. M. (2001). Fluoride release from glass

ionomer activated with fluoride solutions. J Dent Res, 80(5), 1402-1406.

99

Dillman, D. (2007). Mail and Internet surveys- The Tailored Design Method (2nd Edition ed.):

John Wiley& Sons, Inc.

Dogon, I. L. (1990). Present and future value of dental composite materials and sealants. Int J

Technol Assess Health Care, 6(3), 369-377.

Donetti, E., Bedoni, M., Guzzi, G., Pigatto, P., & Sforza, C. (2008). Burning mouth syndrome

possibly linked with an amalgam tattoo: clinical and ultrastructural evidence. Eur J

Dermatol, 18(6), 723-724.

Donly, K. J., & Nelson, J. J. (1997). Fluoride release of restorative materials exposed to a

fluoridated dentifrice. ASDC J Dent Child, 64(4), 249-250.

Donly, K. J., Segura, A., Kanellis, M., & Erickson, R. L. (1999). Clinical performance and caries

inhibition of resin-modified glass ionomer cement and amalgam restorations. J Am Dent

Assoc, 130(10), 1459-1466.

Duffy, M. E. (2002). Methodological issues in Web-based research. J Nurs Scholarsh, 34(1), 83-

88.

Dunlop, R. M., Sanders, B. J., Jones, J. E., Walker, L. A., & Caldwell, R. L. (2013). Pulp therapy

in pediatric patients with congenital heart disease: survey of American Academy of

Pediatric Dentistry members. J Dent Child (Chic), 80(3), 139-144.

Dye, B. A., Arevalo, O., & Vargas, C. M. (2010). Trends in paediatric dental caries by poverty

status in the United States, 1988-1994 and 1999-2004. Int J Paediatr Dent, 20(2), 132-

143. doi: 10.1111/j.1365-263X.2009.01029.x

Eley, B. M. (1997). The future of dental amalgam: a review of the literature. Part 1: Dental

amalgam structure and corrosion. Br Dent J, 182(7), 247-249.

Ellison, R., Green, C., Gibson, J., & Ghaffar, S. (2013). Orofacial granulomatosis related to

amalgam fillings. Scott Med J, 58(4), e24-25. doi: 10.1177/0036933013508049

Elwyn, G., Frosch, D., Thomson, R., Joseph-Williams, N., Lloyd, A., Kinnersley, P., . . . Barry,

M. (2012). Shared decision making: a model for clinical practice. J Gen Intern Med,

27(10), 1361-1367. doi: 10.1007/s11606-012-2077-6

Environment Canada, H. C. (2008). Screening Assessment for the Challenge Phenol, 4,4 ' (1-

methylethylidene) bis (Bisphenol A) Chemical Abstracts Service Registry Number 80-

05-7.

Environment, N. M. o. t. (2006-2007). Working together towards a non-toxic environment and a

safer future- Norway's chemical policy.

Retrieved from

http://www.regjeringen.no/pages/2039888/PDFS/STM200620070014000EN_PDFS.pdf.

100

Ersin, N. K., Candan, U., Aykut, A., Oncag, O., Eronat, C., & Kose, T. (2006). A clinical

evaluation of resin-based composite and glass ionomer cement restorations placed in

primary teeth using the ART approach: results at 24 months. J Am Dent Assoc, 137(11),

1529-1536.

Espelid, I., Cairns, J., Askildsen, J. E., Qvist, V., Gaarden, T., & Tveit, A. B. (2006). Preferences

over dental restorative materials among young patients and dental professionals. Eur J

Oral Sci, 114(1), 15-21. doi: 10.1111/j.1600-0722.2006.00282.x

Espelid, I., & Tveit, A. B. (2001). A comparison of radiographic occlusal and approximal caries

diagnoses made by 240 dentists. Acta Odontol Scand, 59(5), 285-289.

Espelid, I., Tveit, A. B., Mejare, I., Sundberg, H., & Hallonsten, A. L. (2001). Restorative

treatment decisions on occlusal caries in Scandinavia. Acta Odontol Scand, 59(1), 21-27.

Espelid, I., Tveit, A. B., Tornes, K. H., & Alvheim, H. (1999). Clinical behaviour of glass

ionomer restorations in primary teeth. J Dent, 27(6), 437-442.

Evans, S. J. (1991). Good surveys guide. BMJ, 302(6772), 302-303.

Ewoldsen, N., & Herwig, L. (1998). Decay-inhibiting restorative materials: past and present.

Compend Contin Educ Dent, 19(10), 981-984, 986, 988 passim; quiz 992.

Eysenbach, G., & Till, J. E. (2001). Ethical issues in qualitative research on internet

communities. BMJ, 323(7321), 1103-1105.

Fawcett, J., & Buhle, E. L., Jr. (1995). Using the Internet for data collection. An innovative

electronic strategy. Comput Nurs, 13(6), 273-279.

Feinberg, E., Swartz, K., Zaslavsky, A., Gardner, J., & Walker, D. K. (2002). Family income and

the impact of a children's health insurance program on reported need for health services

and unmet health need. Pediatrics, 109(2), E29.

Fishman, R. G., M; Bimstein, E; . (2006). Children's Selection of Posterior Restorative Materials.

J Clin Pediatr Dent, 31(1), 1-4.

Fleisch, A. F., Sheffield, P. E., Chinn, C., Edelstein, B. L., & Landrigan, P. J. (2010). Bisphenol

A and related compounds in dental materials. Pediatrics, 126(4), 760-768. doi:

10.1542/peds.2009-2693

Flores-Mir, C., Palmer, N. G., Northcott, H. C., Huston, C., & Major, P. W. (2006). Computer

and Internet usage by Canadian dentists. J Can Dent Assoc, 72(2), 145.

Folwaczny, M., Loher, C., Mehl, A., Kunzelmann, K. H., & Hickel, R. (2001). Class V lesions

restored with four different tooth-colored materials--3-year results. Clin Oral Investig,

5(1), 31-39.

101

Folwaczny, M., Loher, C., Mehl, A., Kunzelmann, K. H., & Hinkel, R. (2000). Tooth-colored

filling materials for the restoration of cervical lesions: a 24-month follow-up study. Oper

Dent, 25(4), 251-258.

Forss, H., & Widstrom, E. (2001). From amalgam to composite: selection of restorative materials

and restoration longevity in Finland. Acta Odontol Scand, 59(2), 57-62.

Forss, H., & Widstrom, E. (2003). The post-amalgam era: a selection of materials and their

longevity in the primary and young permanent dentitions. Int J Paediatr Dent, 13(3),

158-164.

Forsten, L. (1990). Short- and long-term fluoride release from glass ionomers and other fluoride-

containing filling materials in vitro. Scand J Dent Res, 98(2), 179-185.

Forsten, L. (1994). Fluoride release of glass ionomers. J Esthet Dent, 6(5), 216-222.

Forte, G., Petrucci, F., & Bocca, B. (2008). Metal allergens of growing significance:

epidemiology, immunotoxicology, strategies for testing and prevention. Inflamm Allergy

Drug Targets, 7(3), 145-162.

Frencken, J. E., Pilot, T., Songpaisan, Y., & Phantumvanit, P. (1996). Atraumatic restorative

treatment (ART): rationale, technique, and development. J Public Health Dent, 56(3 Spec

No), 135-140; discussion 161-133.

Fuks, A. B. (2002). The use of amalgam in pediatric dentistry. Pediatr Dent, 24(5), 448-455.

Fuks, A. B. (2005). Status of amalgams in pediatric dentistry: pros and cons. Alpha Omegan,

98(4), 26-32.

Fuks, A. B., Araujo, F. B., Osorio, L. B., Hadani, P. E., & Pinto, A. S. (2000). Clinical and

radiographic assessment of Class II esthetic restorations in primary molars. Pediatr Dent,

22(6), 479-485.

Fukuyama, T., Oda, S., Yamashita, H., Sekiguchi, H., & Yakushiji, M. (2008). Clinical survey

on type of restoration in deciduous teeth. Bull Tokyo Dent Coll, 49(1), 41-50.

Fung, E. Y., Ewoldsen, N. O., St Germain, H. A., Jr., Marx, D. B., Miaw, C. L., Siew, C., . . .

Meyer, D. M. (2000). Pharmacokinetics of bisphenol A released from a dental sealant. J

Am Dent Assoc, 131(1), 51-58.

Geier, D. A., King, P. G., Sykes, L. K., & Geier, M. R. (2008). A comprehensive review of

mercury provoked autism. Indian J Med Res, 128(4), 383-411.

Gergely, E. J. (1989). Desmond Greer Walker Award. Rubber dam acceptance. Br Dent J,

167(7), 249-252.

102

Gilbert, G. H., Litaker, M. S., Pihlstrom, D. J., Amundson, C. W., Gordan, V. V., & Group, D.

C. (2010). Rubber dam use during routine operative dentistry procedures: findings from

the Dental PBRN. Oper Dent, 35(5), 491-499. doi: 10.2341/09-287C

Gjorgievska, E. (2011). Clinical performance of fluoride-releasing dental restoratives. Prilozi,

32(1), 283-294.

Gjorgievska, E., Nicholson, J. W., Iljovska, S., & Slipper, I. J. (2008). Marginal adaptation and

performance of bioactive dental restorative materials in deciduous and young permanent

teeth. J Appl Oral Sci, 16(1), 1-6.

Goldberg, J., Tanzer, J., Munster, E., Amara, J., Thal, F., & Birkhed, D. (1981). Cross-sectional

clinical evaluation of recurrent enamel caries, restoration of marginal integrity, and oral

hygiene status. J Am Dent Assoc, 102(5), 635-641.

Goldman, L. R., Shannon, M. W., & American Academy of Pediatrics: Committee on

Environmental, H. (2001). Technical report: mercury in the environment: implications for

pediatricians. Pediatrics, 108(1), 197-205.

Gravel, K., Legare, F., & Graham, I. D. (2006). Barriers and facilitators to implementing shared

decision-making in clinical practice: a systematic review of health professionals'

perceptions. Implement Sci, 1, 16. doi: 10.1186/1748-5908-1-16

Greenlaw, C., & Brown-Welty, S. (2009). A comparison of web-based and paper-based survey

methods: testing assumptions of survey mode and response cost. Eval Rev, 33(5), 464-

480. doi: 10.1177/0193841X09340214

Gryst, M. E., & Mount, G. J. (1999). The use of glass ionomer in special needs patients. Aust

Dent J, 44(4), 268-274.

Guelmann, M., & Mjor, I. A. (2002). Materials and techniques for restoration of primary molars

by pediatric dentists in Florida. Pediatr Dent, 24(4), 326-331.

Guelmann, M., Mjor, I. A., & Jerrell, G. R. (2001). The teaching of Class I and II restorations in

primary molars: a survey of North American dental schools. Pediatr Dent, 23(5), 410-

414.

Hallett, K. B., & Garcia-Godoy, F. (1993). Microleakage of resin-modified glass ionomer

cement restorations: an in vitro study. Dent Mater, 9(5), 306-311.

Harada, M. (1995). Minamata disease: methylmercury poisoning in Japan caused by

environmental pollution. Crit Rev Toxicol, 25(1), 1-24. doi:

10.3109/10408449509089885

Health, A. R. C. f. P. O. (2011). Dental caries trends in Australian school children. Aust Dent J,

56, 227-230.

103

Heise, A. L. (1971). Time required in rubber dam placement. ASDC J Dent Child, 38(2), 116-

117.

Hertz-Picciotto. (2010). Blood mercury cocnentrations in CHARGE study children with and

without autism. Environ Health Perspect, January 118(1), 161-166.

Hickel, R., Kaaden, C., Paschos, E., Buerkle, V., Garcia-Godoy, F., & Manhart, J. (2005).

Longevity of occlusally-stressed restorations in posterior primary teeth. Am J Dent, 18(3),

198-211.

Hickel, R., & Voss, A. (1990). A comparison of glass cermet cement and amalgam restorations

in primary molars. ASDC J Dent Child, 57(3), 184-188.

Hill, E. E., & Rubel, B. S. (2008). Do dental educators need to improve their approach to

teaching rubber dam use? J Dent Educ, 72(10), 1177-1181.

Holland, I. S., Walls, A. W., Wallwork, M. A., & Murray, J. J. (1986). The longevity of

amalgam restorations in deciduous molars. Br Dent J, 161(7), 255-258.

Horsted-Bindslev, P., Heyde-Petersen, B., Simonsen, P., & Baelum, V. (2005). Tunnel or saucer-

shaped restorations: a survival analysis. Clin Oral Investig, 9(4), 233-238. doi:

10.1007/s00784-005-0011-6

Howard. (2010). Relationships between conversion, temperature, and optical properties during

composite photopolymerization. Acta Biomater, 6, 2053-2059.

Hse, K. M., & Wei, S. H. (1997). Clinical evaluation of compomer in primary teeth: 1-year

results. J Am Dent Assoc, 128(8), 1088-1096.

Huggins, H. A. (2007). Medical implications of dental mercury: a review. Explore (NY), 3(2),

110-117. doi: 10.1016/j.explore.2006.12.008

Hujoel, P. P., Lydon-Rochelle, M., Bollen, A. M., Woods, J. S., Geurtsen, W., & del Aguila, M.

A. (2005). Mercury exposure from dental filling placement during pregnancy and low

birth weight risk. Am J Epidemiol, 161(8), 734-740. doi: 10.1093/aje/kwi100

Hunter, B. (1985). Survival of dental restorations in young patients. Community Dent Oral

Epidemiol, 13(5), 285-287.

Ingalls, T. H. (1986). Endemic clustering of multiple sclerosis in time and place, 1934-1984.

Confirmation of a hypothesis. Am J Forensic Med Pathol, 7(1), 3-8.

Innes, N. P., Ricketts, D. N., & Evans, D. J. (2007). Preformed metal crowns for decayed

primary molar teeth. Cochrane Database Syst Rev(1), CD005512. doi:

10.1002/14651858.CD005512.pub2

ISAPS. (2011). ISAPS International Survey on Aesthetic/Cosmetic Procedures Performed in

2011.

104

Jackson, R. D., & Morgan, M. (2000). The new posterior resins and a simplified placement

technique. J Am Dent Assoc, 131(3), 375-383.

Jones, C. M., & Reid, J. S. (1988). Patient and operator attitudes toward rubber dam. ASDC J

Dent Child, 55(6), 452-454.

Jones, D. W. (1999). Exposure or absorption and the crucial question of limits for mercury. J

Can Dent Assoc, 65(1), 42-46.

Joseph, R. (2005). The Father of Modern Dentistry- Dr. Greene Vardiman Black (1836-1915). J

Conserv Dent, 8, 5-6.

Juntgen, L. M., Sanders, B. J., Walker, L. A., Jones, J. E., Weddell, J. A., Tomlin, A. M., . . .

Maupome, G. (2013). Factors influencing behavior guidance: a survey of practicing

pediatric dentists. Pediatr Dent, 35(7), 539-545.

Kal, B. I., Evcin, O., Dundar, N., Tezel, H., & Unal, I. (2008). An unusual case of immediate

hypersensitivity reaction associated with an amalgam restoration. Br Dent J, 205(10),

547-550. doi: 10.1038/sj.bdj.2008.981

Kanerva, L., Alanko, K., Estlander, T., Jolanki, R., Lahtinen, A., & Savela, A. (2000). Statistics

on occupational contact dermatitis from (meth)acrylates in dental personnel. Contact

Dermatitis, 42(3), 175-176.

Kapitan, M., Sustova, Z., Ivancakova, R., & Suchanek, J. (2014). A comparison of different

rubber dam systems on a dental simulator. Acta Medica (Hradec Kralove), 57(1), 15-20.

Kaplan, S. H., Greenfield, S., Gandek, B., Rogers, W. H., & Ware, J. E., Jr. (1996).

Characteristics of physicians with participatory decision-making styles. Ann Intern Med,

124(5), 497-504.

Kavvadia, K., Kakaboura, A., Vanderas, A. P., & Papagiannoulis, L. (2004). Clinical evaluation

of a compomer and an amalgam primary teeth class II restorations: a 2-year comparative

study. Pediatr Dent, 26(3), 245-250.

Kenney, G. M., Marton, J., Klein, A. E., Pelletier, J. E., & Talbert, J. (2011). The effects of

Medicaid and CHIP policy changes on receipt of preventive care among children. Health

Serv Res, 46(1 Pt 2), 298-318. doi: 10.1111/j.1475-6773.2010.01199.x

Khordi-Mood, M., Sarraf-Shirazi, A. R., & Balali-Mood, M. (2001). Urinary mercury excretion

following amalgam filling in children. J Toxicol Clin Toxicol, 39(7), 701-705.

Kiesler, D. J., & Auerbach, S. M. (2006). Optimal matches of patient preferences for

information, decision-making and interpersonal behavior: evidence, models and

interventions. Patient Educ Couns, 61(3), 319-341. doi: 10.1016/j.pec.2005.08.002

Kilpatrick, N. M., Murray, J. J., & McCabe, J. F. (1995). The use of a reinforced glass-ionomer

cermet for the restoration of primary molars: a clinical trial. Br Dent J, 179(5), 175-179.

105

Kilpatrick, N. M., & Neumann, A. (2007). Durability of amalgam in the restoration of class II

cavities in primary molars: a systematic review of the literature. Eur Arch Paediatr Dent,

8(1), 5-13.

Kim, K. H., Ong, J. L., & Okuno, O. (2002). The effect of filler loading and morphology on the

mechanical properties of contemporary composites. J Prosthet Dent, 87(6), 642-649.

Kingman, A., Albers, J. W., Arezzo, J. C., Garabrant, D. H., & Michalek, J. E. (2005). Amalgam

exposure and neurological function. Neurotoxicology, 26(2), 241-255. doi:

10.1016/j.neuro.2004.09.008

Kittleson, M. (1997). Determining effective follow-up of e-mail surveys. American Journal of

Health Behavior, 21(3), 193-196.

Knight, G. T., Berry, T. G., Barghi, N., & Burns, T. R. (1993). Effects of two methods of

moisture control on marginal microleakage between resin composite and etched enamel:

a clinical study. Int J Prosthodont, 6(5), 475-479.

Kovarik, R. E. (2009). Restoration of posterior teeth in clinical practice: evidence base for

choosing amalgam versus composite. Dent Clin North Am, 53(1), 71-76, ix. doi:

10.1016/j.cden.2008.11.001

Kremers, L., Halbach, S., Willruth, H., Mehl, A., Welzl, G., Wack, F. X., . . . Greim, H. (1999).

Effect of rubber dam on mercury exposure during amalgam removal. Eur J Oral Sci,

107(3), 202-207.

Kugel, G., & Ferrari, M. (2000). The science of bonding: from first to sixth generation. J Am

Dent Assoc, 131 Suppl, 20S-25S.

Laeijendecker, R., Dekker, S. K., Burger, P. M., Mulder, P. G., Van Joost, T., & Neumann, M.

H. (2004). Oral lichen planus and allergy to dental amalgam restorations. Arch Dermatol,

140(12), 1434-1438. doi: 10.1001/archderm.140.12.1434

Lauterbach, M., Martins, I. P., Castro-Caldas, A., Bernardo, M., Luis, H., Amaral, H., . . .

Derouen, T. (2008). Neurological outcomes in children with and without amalgam-

related mercury exposure: seven years of longitudinal observations in a randomized trial.

J Am Dent Assoc, 139(2), 138-145.

Lennon, A. M., Wiegand, A., Buchalla, W., & Attin, T. (2007). Approximal caries development

in surfaces in contact with fluoride-releasing and non-fluoride-releasing restorative

materials: an in situ study. Eur J Oral Sci, 115(6), 497-501. doi: 10.1111/j.1600-

0722.2007.00495.x

Letzel, H., van 't Hof, M. A., Vrijhoef, M. M., Marshall, G. W., Jr., & Marshall, S. J. (1989). A

controlled clinical study of amalgam restorations: survival, failures, and causes of failure.

Dent Mater, 5(2), 115-121.

106

Levering, N. J., & Messer, L. B. (1988). The durability of primary molar restorations: I.

Observations and predictions of success of amalgams. Pediatr Dent, 10(2), 74-80.

Levy, M., Schwartz, S., Dijak, M., Weber, J. P., Tardif, R., & Rouah, F. (2004). Childhood urine

mercury excretion: dental amalgam and fish consumption as exposure factors. Environ

Res, 94(3), 283-290. doi: 10.1016/j.envres.2003.07.004

Luglie, P. F., Campus, G., Chessa, G., Spano, G., Capobianco, G., Fadda, G. M., & Dessole, S.

(2005). Effect of amalgam fillings on the mercury concentration in human amniotic fluid.

Arch Gynecol Obstet, 271(2), 138-142. doi: 10.1007/s00404-003-0578-6

Lynch, C. D. (2007). Trends in the placement of posterior composites in dental schools. J Dent

Educ, 71(3), 430-434.

Lynch, C. D., Frazier, K. B., McConnell, R. J., Blum, I. R., & Wilson, N. H. (2011). Minimally

invasive management of dental caries: contemporary teaching of posterior resin-based

composite placement in U.S. and Canadian dental schools. J Am Dent Assoc, 142(6), 612-

620.

Lynch, C. D., & McConnell, R. J. (2007). Attitudes and use of rubber dam by Irish general

dental practitioners. Int Endod J, 40(6), 427-432. doi: 10.1111/j.1365-2591.2007.01212.x

Lynch, C. D., McConnell, R. J., & Wilson, N. H. (2006a). Teaching of posterior composite resin

restorations in undergraduate dental schools in Ireland and the United Kingdom. Eur J

Dent Educ, 10(1), 38-43. doi: 10.1111/j.1600-0579.2006.00394.x

Lynch, C. D., McConnell, R. J., & Wilson, N. H. (2006b). Teaching the placement of posterior

resin-based composite restorations in U.S. dental schools. J Am Dent Assoc, 137(5), 619-

625.

Lyttle, H. A., & Bowden, G. H. (1993). The level of mercury in human dental plaque and

interaction in vitro between biofilms of Streptococcus mutans and dental amalgam. J

Dent Res, 72(9), 1320-1324.

Mackert, J. R., Jr. (1991). Dental amalgam and mercury. J Am Dent Assoc, 122(8), 54-61.

Mackert, J. R., Jr., & Wahl, M. J. (2004). Are there acceptable alternatives to amalgam? J Calif

Dent Assoc, 32(7), 601-610.

Makhija, S. K., Gordan, V. V., Gilbert, G. H., Litaker, M. S., Rindal, D. B., Pihlstrom, D. J., . . .

Dental Practice-Based Research Network Collaborative, G. (2011). Practitioner, patient

and carious lesion characteristics associated with type of restorative material: findings

from The Dental Practice-Based Research Network. J Am Dent Assoc, 142(6), 622-632.

Mala, S., Lynch, C. D., Burke, F. M., & Dummer, P. M. (2009). Attitudes of final year dental

students to the use of rubber dam. Int Endod J, 42(7), 632-638. doi: 10.1111/j.1365-

2591.2009.01569.x

107

Mandari, G. J., Frencken, J. E., & van't Hof, M. A. (2003). Six-year success rates of occlusal

amalgam and glass-ionomer restorations placed using three minimal intervention

approaches. Caries Res, 37(4), 246-253. doi: 70866

Manuja, N., Pandit, I. K., Srivastava, N., Gugnani, N., & Nagpal, R. (2011). Comparative

evaluation of shear bond strength of various esthetic restorative materials to dentin: an in

vitro study. J Indian Soc Pedod Prev Dent, 29(1), 7-13. doi: 10.4103/0970-4388.79913

Mass, E., Gordon, M., & Fuks, A. B. (1999). Assessment of compomer proximal restorations in

primary molars: a retrospective study in children. ASDC J Dent Child, 66(2), 93-97, 84.

McComb, D. (2005). Class I and Class II silver amalgam and resin composite posterior

restorations: teaching approaches in Canadian faculties of dentistry. J Can Dent Assoc,

71(6), 405-406.

McCreery, A. M., & Truelove, E. (1991). Decision making in dentistry. Part I: A historical and

methodological overview. J Prosthet Dent, 65(3), 447-451.

McLean, J. W., Nicholson, J. W., & Wilson, A. D. (1994). Proposed nomenclature for glass-

ionomer dental cements and related materials. Quintessence Int, 25(9), 587-589.

McLean, J. W., Powis, D. R., Prosser, H. J., & Wilson, A. D. (1985). The use of glass-ionomer

cements in bonding composite resins to dentine. Br Dent J, 158(11), 410-414.

McParland, H., & Warnakulasuriya, S. (2012). Oral lichenoid contact lesions to mercury and

dental amalgam--a review. J Biomed Biotechnol, 2012, 589569. doi:

10.1155/2012/589569

Meyer, J. M., Cattani-Lorente, M. A., & Dupuis, V. (1998). Compomers: between glass-ionomer

cements and composites. Biomaterials, 19(6), 529-539.

Micik, R. E., Miller, R. L., Mazzarella, M. A., & Ryge, G. (1969). Studies on dental aerobiology.

I. Bacterial aerosols generated during dental procedures. J Dent Res, 48(1), 49-56.

Mileman, P. A., & van der Weele, L. T. (1996). The role of caries recognition: treatment

decisions from bitewing radiographs. Dentomaxillofac Radiol, 25(5), 228-233. doi:

10.1259/dmfr.25.5.9161175

Mills, I., Frost, J., Cooper, C., Moles, D. R., & Kay, E. (2014). Patient-centred care in general

dental practice--a systematic review of the literature. BMC Oral Health, 14, 64. doi:

10.1186/1472-6831-14-64

Mitchell, C. D., WH. (1997). Comparison of the porosity of hand-mixed and capsulated glass-

ionomer luting cements. Biomaterials, 18(16), 1127-1131.

Mitchell, R. J., Koike, M., & Okabe, T. (2007). Posterior amalgam restorations--usage,

regulation, and longevity. Dent Clin North Am, 51(3), 573-589, v. doi:

10.1016/j.cden.2007.04.004

108

Mitra, S. B., Wu, D., & Holmes, B. N. (2003). An application of nanotechnology in advanced

dental materials. J Am Dent Assoc, 134(10), 1382-1390.

Mjor, I. A. (1997). The reasons for replacement and the age of failed restorations in general

dental practice. Acta Odontol Scand, 55(1), 58-63.

Mjor, I. A., Dahl, J. E., & Moorhead, J. E. (2002). Placement and replacement of restorations in

primary teeth. Acta Odontol Scand, 60(1), 25-28.

Momoi, Y., & McCabe, J. F. (1993). Fluoride release from light-activated glass ionomer

restorative cements. Dent Mater, 9(3), 151-154.

Monroe, B. M., & Weiner, S. A. (1969). Mechanisms of photochemical reactions in

solution.VIII- Photoreduction of camphorquinone. J Am Chem Soc, 91, 450-456.

Morrier, J. J., Suchett-Kaye, G., Nguyen, D., Rocca, J. P., Blanc-Benon, J., & Barsotti, O.

(1998). Antimicrobial activity of amalgams, alloys and their elements and phases. Dent

Mater, 14(2), 150-157.

Morton, H. E., North, L. L., Jr., & Engley, F. B., Jr. (1948). The bacteriostatic and bactericidal

actions of some mercurial compounds on hemolytic streptococci; in vivo and in vitro

studies. Bull Am Soc Hosp Pharm, 5(1), 21-25.

Moszner. (2004). Nanotechnology for dental composites. Int J Nanotechnology, 1, 130-156.

Nicolae, Ames, & Quinonez. (2013). Dental amalgam and urinary mercury concentrations: a

descriptive study. BMC Oral Health, 13, 44. doi: 10.1186/1472-6831-13-44

Nicolae, A. (2010). An Analysis of the Relationship between Urinary Merucry levels and the

Number of Dental Amalgam Restoration Surfaces in a representative Group of the

Canadan Population. (MSc), University of Toronto.

Nomoto, R., Uchida, K., & Hirasawa, T. (1994). Effect of light intensity on polymerization of

light-cured composite resins. Dent Mater J, 13(2), 198-205.

Nordbo, H., Leirskar, J., & von der Fehr, F. R. (1998). Saucer-shaped cavity preparations for

posterior approximal resin composite restorations: observations up to 10 years.

Quintessence Int, 29(1), 5-11.

Nyheter, S. (2007, December 29, 2007. Updated February 19, 2014.). Amalgam and mercury

banned, SvD Nyheter. Retrieved from http://www.svd.se/nyheter/inrikes/amalgam-och-

kvicksilver-forbjuds_724369.svd

OHG. (2008). Welcome to the 2008 Pacific Dental Conference. Retrieved August 16, 2008,

from http://www.oralhealthgroup.com/news/welcome-to-the-2008-pacific-dental-

conference/1000218994/?type=Print%20Archives

109

Ohiomoba, H. O., & Nelson, L. P. (2013). A performance measurement plan for pediatric

dentists: using accuracy of caries diagnosis from intraoral radiographs. Pediatr Dent,

35(1), 27-32.

Opdam, N. J., Bronkhorst, E. M., Loomans, B. A., & Huysmans, M. C. (2010). 12-year survival

of composite vs. amalgam restorations. J Dent Res, 89(10), 1063-1067. doi:

10.1177/0022034510376071

Ostlund, J., Moller, K., & Koch, G. (1992). Amalgam, composite resin and glass ionomer cement

in Class II restorations in primary molars--a three year clinical evaluation. Swed Dent J,

16(3), 81-86.

Pair, R. L., Udin, R. D., & Tanbonliong, T. (2004). Materials used to restore class II lesions in

primary molars: a survey of California pediatric dentists. Pediatr Dent, 26(6), 501-507.

Palkovicova, L., Ursinyova, M., Masanova, V., Yu, Z., & Hertz-Picciotto, I. (2008). Maternal

amalgam dental fillings as the source of mercury exposure in developing fetus and

newborn. J Expo Sci Environ Epidemiol, 18(3), 326-331. doi: 10.1038/sj.jes.7500606

Palotie, U. (2009). Restorative treatment practices and dentist-related factors (Academic

Dissertation), University of Helsinki, Helsinki, Finland

Palotie, U., & Vehkalahti, M. M. (2009). Finnish dentists' perceptions of the longevity of direct

dental restorations. Acta Odontol Scand, 67(1), 44-49. doi: 10.1080/00016350802577792

Papathanasiou, A. G., Curzon, M. E., & Fairpo, C. G. (1994). The influence of restorative

material on the survival rate of restorations in primary molars. Pediatr Dent, 16(4), 282-

288.

Parashos, P., Morgan, M. V., & Messer, H. H. (2005). Response rate and nonresponse bias in a

questionnaire survey of dentists. Community Dent Oral Epidemiol, 33(1), 9-16. doi:

10.1111/j.1600-0528.2004.00181.x

Park, S. H., & Lee, C. S. (1996). The difference in degree of conversion between light-cured and

additional heat-cured composites. Oper Dent, 21(5), 213-217.

Paschoal, M. A., Gurgel, C. V., Rios, D., Magalhaes, A. C., Buzalaf, M. A., & Machado, M. A.

(2011). Fluoride release profile of a nanofilled resin-modified glass ionomer cement.

Braz Dent J, 22(4), 275-279.

Peutzfeldt, A. (1994). Correlation between recordings obtained with a light-intensity tester and

degree of conversion of a light-curing resin. Scand J Dent Res, 102(1), 73-75.

Pezelj-Ribaric, S., Prpic, J., Miletic, I., Brumini, G., Soskic, M. S., & Anic, I. (2008).

Association between oral lichenoid reactions and amalgam restorations. J Eur Acad

Dermatol Venereol, 22(10), 1163-1167. doi: 10.1111/j.1468-3083.2008.02736.x

110

Pohl, L., & Bergman, M. (1995). The dentist's exposure to elemental mercury vapor during

clinical work with amalgam. Acta Odontol Scand, 53(1), 44-48.

Policy, D. H. S. V. (1999). Use of dental amalgam.

Qvist, V., Laurberg, L., Poulsen, A., & Teglers, P. T. (1997). Longevity and cariostatic effects of

everyday conventional glass-ionomer and amalgam restorations in primary teeth: three-

year results. J Dent Res, 76(7), 1387-1396.

Qvist, V., Laurberg, L., Poulsen, A., & Teglers, P. T. (2004). Eight-year study on conventional

glass ionomer and amalgam restorations in primary teeth. Acta Odontol Scand, 62(1), 37-

45.

Qvist, V., Qvist, J., & Mjor, I. A. (1990). Placement and longevity of tooth-colored restorations

in Denmark. Acta Odontol Scand, 48(5), 305-311.

Randall, R. C., Vrijhoef, M. M., & Wilson, N. H. (2000). Efficacy of preformed metal crowns

vs. amalgam restorations in primary molars: a systematic review. J Am Dent Assoc,

131(3), 337-343.

Randall, R. C., Vrijhoef, M. M., & Wilson, N. H. (2002). Current trends in restorative dentistry

in the UK: a Delphi approach. J Dent, 30(4), 177-187.

Rasines Alcaraz, M. G., Veitz-Keenan, A., Sahrmann, P., Schmidlin, P. R., Davis, D., &

Iheozor-Ejiofor, Z. (2014). Direct composite resin fillings versus amalgm fillings for

permanent or adult posterior teeth. Cochrane Database Syst Rev, 3(Art No.: CD005620).

doi: 10.1002/14651858.CD005620.pub2

Reuters. (2008). Dental Mercury Use Banned in Norway, Sweden, and Denmark because

composites are adequate replacements.

Rho, Y. J., Namgung, C., Jin, B. H., Lim, B. S., & Cho, B. H. (2013). Longevity of direct

restorations in stress-bearing posterior cavities: a retrospective study. Oper Dent, 38(6),

572-582. doi: 10.2341/12-432-C

Richards, T. (1999). Patients' priorities. BMJ, 318(7179), 277.

Richardson, G. (1995). Assessment of Mercury Exposure and Risks from Dental Amalgam.

Medical Devises Bureau with Environmental Health Directorate of Health Canada. Final

report.

Ring, J. A., Ghabrial, H., Ching, M. S., Smallwood, R. A., & Morgan, D. J. (1999). Fetal hepatic

drug elimination. Pharmacol Ther, 84(3), 429-445.

Robertello, F. J., Coffey, J. P., Lynde, T. A., & King, P. (1999). Fluoride release of glass

ionomer-based luting cements in vitro. J Prosthet Dent, 82(2), 172-176.

111

Roberts, J. F., & Sherriff, M. (1990). The fate and survival of amalgam and preformed crown

molar restorations placed in a specialist paediatric dental practice. Br Dent J, 169(8), 237-

244.

Roberts, M. C., Leroux, B. G., Sampson, J., Luis, H. S., Bernardo, M., & Leitao, J. (2008).

Dental amalgam and antibiotic- and/or mercury-resistant bacteria. J Dent Res, 87(5), 475-

479.

Rosenstiel, S. F., Land, M. F., & Rashid, R. G. (2004). Dentists' molar restoration choices and

longevity: a web-based survey. J Prosthet Dent, 91(4), 363-367. doi:

10.1016/S0022391304000502

Ruse, N. D. (1999). What is a "compomer"? J Can Dent Assoc, 65(9), 500-504.

Rutar, J., McAllan, L., & Tyas, M. J. (2002). Three-year clinical performance of glass ionomer

cement in primary molars. Int J Paediatr Dent, 12(2), 146-147.

Ruyter, E. (1985). [Composite dental restorative materials]. Tandlaegebladet, 89(2), 67-70.

Ruyter, I. E., & Oysaed, H. (1982). Conversion in different depths of ultraviolet and visible light

activated composite materials. Acta Odontol Scand, 40(3), 179-192.

Sandner, B., Baudach, S., Davy, K. W., Braden, M., & Clarke, R. L. (1997). Synthesis of

BISGMA derivatives, properties of their polymers and composites. J Mater Sci Mater

Med, 8(1), 39-44.

Santerre. (2007). Bisphenol A: What dentists should know and tell their patients. J Canadian

Dental Association, 73(7), 563.

Sasaki, N., Okuda, K., Kato, T., Kakishima, H., Okuma, H., Abe, K., . . . Kubono, K. (2005).

Salivary bisphenol-A levels detected by ELISA after restoration with composite resin. J

Mater Sci Mater Med, 16(4), 297-300. doi: 10.1007/s10856-005-0627-8

Say, R., Murtagh, M., & Thomson, R. (2006). Patients' preference for involvement in medical

decision making: a narrative review. Patient Educ Couns, 60(2), 102-114. doi:

10.1016/j.pec.2005.02.003

Scarbecz, M. (2012). 'Nudging' your patients toward improved oral health. J Am Dent Assoc,

143(8), 907-915.

Schleyer, T. K., & Forrest, J. L. (2000). Methods for the design and administration of web-based

surveys. J Am Med Inform Assoc, 7(4), 416-425.

Seale, N. S. (2002). The use of stainless steel crowns. Pediatr Dent, 24(5), 501-505.

Services, U. D. o. H. a. H. (2000). A Report of the Surgeon General. Rockville, MD: US

Department of Health and HUman Services, National Institute of Dental and

Craniofacial Research. National Institutes of Health.

112

Sharaf, A. A., & Farsi, N. M. (2004). A clinical and radiographic evaluation of stainless steel

crowns for primary molars. J Dent, 32(1), 27-33.

Shenker, B. J., Maserejian, N. N., Zhang, A., & McKinlay, S. (2008). Immune function effects of

dental amalgam in children: a randomized clinical trial. J Am Dent Assoc, 139(11), 1496-

1505.

Shenoy, A. (2008). Is it the end of the road for dental amalgam? A critical review. J Conserv

Dent, 11(3), 99-107. doi: 10.4103/0972-0707.45247

Sideridou, I. D., & Achilias, D. S. (2005). Elution study of unreacted Bis-GMA, TEGDMA,

UDMA, and Bis-EMA from light-cured dental resins and resin composites using HPLC.

J Biomed Mater Res B Appl Biomater, 74(1), 617-626. doi: 10.1002/jbm.b.30252

Silver, S. (2003). Bacterial silver resistance: molecular biology and uses and misuses of silver

compounds. FEMS Microbiol Rev, 27(2-3), 341-353.

Simmons, J. J. (1983). The miracle mixture. Glass ionomer and alloy powder. Tex Dent J,

100(10), 6-12.

Singh, J. A., Sloan, J. A., Atherton, P. J., Smith, T., Hack, T. F., Huschka, M. M., . . . Degner, L.

F. (2010). Preferred roles in treatment decision making among patients with cancer: a

pooled analysis of studies using the Control Preferences Scale. Am J Manag Care, 16(9),

688-696.

Sivaraman, S. S., Hassan, M., & Pearson, J. M. (2013). A national survey of pediatric dentists on

antibiotic use in children. Pediatr Dent, 35(7), 546-549.

Sjogren, P., & Halling, A. (2002). Long-term cost of direct Class II molar restorations. Swed

Dent J, 26(3), 107-114.

Skjelvik, J. M. (2012). Review of Norwegian experiences with the phase-out of dental amalgam

use. http://www.miljodirektoratet.no/old/klif/publikasjoner/2946/ta2946.pdf:

Environmental Agency

Slawinski, D., & Wilson, S. (2010). Rubber dam use: a survey of pediatric dentistry training

programs and private practitioners. Pediatr Dent, 32(1), 64-68.

Smith, D. C., & Ruse, N. D. (1986). Acidity of glass ionomer cements during setting and its

relation to pulp sensitivity. J Am Dent Assoc, 112(5), 654-657.

Smith, W. F. (1990). Materials science and engineering. (Vol. 2nd edition): New York:

McGraw-Hill.

Soderholm, K. J. M. (1985). Posterior Composite Resin Dental Restorative Materials: Ed. Smith

D.C., Peter Szulc Publishing Corporation, Netherlands.

113

Soldani, F., & Foley, J. (2007). An assessment of rubber dam usage amongst specialists in

paediatric dentistry practising within the UK. Int J Paediatr Dent, 17(1), 50-56. doi:

10.1111/j.1365-263X.2006.00796.x

Soncini, J. A., Maserejian, N. N., Trachtenberg, F., Tavares, M., & Hayes, C. (2007). The

longevity of amalgam versus compomer/composite restorations in posterior primary and

permanent teeth: findings From the New England Children's Amalgam Trial. J Am Dent

Assoc, 138(6), 763-772.

Sousa, R. P., Zanin, I. C., Lima, J. P., Vasconcelos, S. M., Melo, M. A., Beltrao, H. C., &

Rodrigues, L. K. (2009). In situ effects of restorative materials on dental biofilm and

enamel demineralisation. J Dent, 37(1), 44-51. doi: 10.1016/j.jdent.2008.08.009

Stock. (1971a). Address given to the Berlin Geselischaft fur Zahnheiikunde, 1926. Reported in:

The use of amalgam for dental fillings (Berlin letter). Abstracted in J Am Dent Assoc, 87,

685-686.

Stock. (1971b). Dangers of mercury, 1926. Abstracted in J Am Dent Assoc(87), 1599.

Sundberg, H., Mejare, I., Espelid, I., & Tveit, A. B. (2000). Swedish dentists' decisions on

preparation techniques and restorative materials. Acta Odontol Scand, 58(3), 135-141.

Sunnegardh-Gronberg, K., van Dijken, J. W., Funegard, U., Lindberg, A., & Nilsson, M. (2009).

Selection of dental materials and longevity of replaced restorations in Public Dental

Health clinics in northern Sweden. J Dent, 37(9), 673-678. doi:

10.1016/j.jdent.2009.04.010

Surkan, P. J., Wypij, D., Trachtenberg, F., Daniel, D. B., Barregard, L., McKinlay, S., &

Bellinger, D. C. (2009). Neuropsychological function in school-age children with low

mercury exposures. Environ Res, 109(6), 728-733. doi: 10.1016/j.envres.2009.04.006

Sustercic, D., Cevc, P., Funuk , N., & Pintar, M. (1993). Determination of curing time in

conversion of light-curing BisGMA-based methacrylate resins. Biomaterials, 14, 871-

875.

Swartz, M. L., Phillips, R. W., & Clark, H. E. (1984). Long-term F release from glass ionomer

cements. J Dent Res, 63(2), 158-160.

Swartz, M. L., Phillips, R. W., Norman, R. D., Elliason, S., Rhodes, B. F., & Clark, H. E. (1976).

Addition of fluoride to pit and fissure sealants--a feasibility study. J Dent Res, 55(5),

757-771.

Szymanska, J. (2007). Dental bioaerosol as an occupational hazard in a dentist's workplace. Ann

Agric Environ Med, 14(2), 203-207.

Talib, R. (1993). Dental composites: a review. J Nihon Univ Sch Dent, 35(3), 161-170.

114

Tam, L. E., Chan, G. P., & Yim, D. (1997). In vitro caries inhibition effects by conventional and

resin-modified glass-ionomer restorations. Oper Dent, 22(1), 4-14.

Tezel, H., Ertas, O. S., Erakin, C., & Kayali, A. (2001). Blood mercury levels of dental students

and dentists at a dental school. Br Dent J, 191(8), 449-452. doi: 10.1038/sj.bdj.4801205a

Tillberg, A., Stenberg, B., & Berglund, A. (2009). Reactions to resin-based dental materials in

patients--type, time to onset, duration, and consequence of the reaction. Contact

Dermatitis, 61(6), 313-319. doi: 10.1111/j.1600-0536.2009.01590.x

Toledano, M., Osorio, E., Osorio, R., & Garcia-Godoy, F. (1999). Microleakage of Class V

resin-modified glass ionomer and compomer restorations. J Prosthet Dent, 81(5), 610-

615.

Tominaga, T., Negishi, T., Hirooka, H., Miyachi, A., Inoue, A., Hayasaka, I., & Yoshikawa, Y.

(2006). Toxicokinetics of bisphenol A in rats, monkeys and chimpanzees by the LC-

MS/MS method. Toxicology, 226(2-3), 208-217. doi: 10.1016/j.tox.2006.07.004

Tomka, M., Machovcova, A., Pelclova, D., Petanova, J., Arenbergerova, M., & Prochazkova, J.

(2011). Orofacial granulomatosis associated with hypersensitivity to dental amalgam.

Oral Surg Oral Med Oral Pathol Oral Radiol Endod, 112(3), 335-341. doi:

10.1016/j.tripleo.2011.03.030

Tran, L. A., & Messer, L. B. (2003). Clinicians' choices of restorative materials for children.

Aust Dent J, 48(4), 221-232.

Tyas, M. J. (1991). Cariostatic effect of glass ionomer cement: a five-year clinical study. Aust

Dent J, 36(3), 236-239.

Tyas, M. J. (2005). Placement and replacement of restorations by selected practitioners. Aust

Dent J, 50(2), 81-89; quiz 127.

Van Meerbeek, B., Vanherle, G., Lesaffre, E., Braem, M., & Lambrechts, P. (1991). Trends in

the selection of dental filling materials. J Dent, 19(4), 207-213.

van Noort, R., Gjerdet, N. R., Schedle, A., Bjorkman, L., & Berglund, A. (2004). An overview of

the current status of national reporting systems for adverse reactions to dental materials. J

Dent, 32(5), 351-358. doi: 10.1016/j.jdent.2004.02.001

Vermeersch, G., Leloup, G., & Vreven, J. (2001). Fluoride release from glass-ionomer cements,

compomers and resin composites. J Oral Rehabil, 28(1), 26-32.

Vidnes-Kopperud, S., Tveit, A. B., Gaarden, T., Sandvik, L., & Espelid, I. (2009). Factors

influencing dentists' choice of amalgam and tooth-colored restorative materials for Class

II preparations in younger patients. Acta Odontol Scand, 67(2), 74-79. doi:

10.1080/00016350802577800

115

Volkel, W., Colnot, T., Csanady, G. A., Filser, J. G., & Dekant, W. (2002). Metabolism and

kinetics of bisphenol a in humans at low doses following oral administration. Chem Res

Toxicol, 15(10), 1281-1287.

Vujicic, M., & Nasseh, K. (2014). A decade in dental care utilization among adults and children

(2001-2010). Health Serv Res, 49(2), 460-480. doi: 10.1111/1475-6773.12130

Wahl, M. J. (2001). Amalgam--Resurrection and redemption. Part 1: the clinical and legal

mythology of anti-amalgam. Quintessence Int, 32(7), 525-535.

Wall, T. P., Vujicic, M., & Nasseh, K. (2012). Recent trends in the utilization of dental care in

the United States. J Dent Educ, 76(8), 1020-1027.

Wataha, J. C., Hanks, C. T., Strawn, S. E., & Fat, J. C. (1994). Cytotoxicity of components of

resins and other dental restorative materials. J Oral Rehabil, 21(4), 453-462.

Welbury, R. R., Shaw, A. J., Murray, J. J., Gordon, P. H., & McCabe, J. F. (2000). Clinical

evaluation of paired compomer and glass ionomer restorations in primary molars: final

results after 42 months. Br Dent J, 189(2), 93-97.

Welbury, R. R., Walls, A. W., Murray, J. J., & McCabe, J. F. (1991). The 5-year results of a

clinical trial comparing a glass polyalkenoate (ionomer) cement restoration with an

amalgam restoration. Br Dent J, 170(5), 177-181.

WHO. (Geneva, 2003). Elemental mercury and Inorganic Mercury Compounds: Human Health

Aspects.

Widstrom, E., & Forss, H. (1994). Selection of restorative materials in dental treatment of

children and adults in public and private dental care in Finland. Swed Dent J, 18(1-2), 1-

7.

Wilder, A. D., Jr., May, K. N., Jr., Bayne, S. C., Taylor, D. F., & Leinfelder, K. F. (1999).

Seventeen-year clinical study of ultraviolet-cured posterior composite Class I and II

restorations. J Esthet Dent, 11(3), 135-142.

Wilkinson, C., Khanji, M., Cotter, P. E., Dunne, O., & O'Keeffe, S. T. (2008). Preferences of

acutely ill patients for participation in medical decision-making. Qual Saf Health Care,

17(2), 97-100. doi: 10.1136/qshc.2006.021378

Wilson, A. D., Prosser, H. J., & Powis, D. M. (1983). Mechanism of adhesion of polyelectrolyte

cements to hydroxyapatite. J Dent Res, 62(5), 590-592.

Wilson, A. D. M., J.W.;. (1988). Glass ionomer cement.

Woods, J. S., Martin, M. D., Leroux, B. G., DeRouen, T. A., Bernardo, M. F., Luis, H. S., . . .

Rue, T. C. (2009). Urinary porphyrin excretion in children with mercury amalgam

treatment: findings from the Casa Pia Children's Dental Amalgam Trial. J Toxicol

Environ Health A, 72(14), 891-896. doi: 10.1080/15287390902959557

116

Wyatt, J. C. (2000). When to use web-based surveys. J Am Med Inform Assoc, 7(4), 426-429.

Xu, X., Ling, L., Wang, R., & Burgess, J. O. (2006). Formulation and characterization of a novel

fluoride-releasing dental composite. Dent Mater, 22(11), 1014-1023. doi:

10.1016/j.dental.2005.11.027

Yap, A. U., Tan, C. H., & Chung, S. M. (2004). Wear behavior of new composite restoratives.

Oper Dent, 29(3), 269-274.

Yengopal, V., Harneker, S. Y., Patel, N., & Siegfried, N. (2009). Dental fillings for the treatment

of caries in the primary dentition. Cochrane Database Syst Rev(2), CD004483. doi:

10.1002/14651858.CD004483.pub2

Yoshida, K., Tanagawa, M., & Atsuta, M. (1999). Characterization and inhibitory effect of

antibacterial dental resin composites incorporating silver-supported materials. J Biomed

Mater Res, 47(4), 516-522.

Zantner, C., Kielbassa, A. M., Martus, P., & Kunzelmann, K. H. (2004). Sliding wear of 19

commercially available composites and compomers. Dent Mater, 20(3), 277-285. doi:

10.1016/S0109-5641(03)00104-0

Zhang, Y., Su, H., Shang, L., Li, D., Wang, R., Zhang, R., & Xu, Y. (2011). Preferences and

perceived involvement in treatment decision making among Chinese patients with

chronic hepatitis. Med Decis Making, 31(2), 245-253. doi: 10.1177/0272989X10375990

Zimmerli, B., Strub, M., Jeger, F., Stadler, O., & Lussi, A. (2010). Composite materials:

composition, properties and clinical applications. A literature review. Schweiz

Monatsschr Zahnmed, 120(11), 972-986.

Zimmerman, J. A., Feigal, R. J., Till, M. J., & Hodges, J. S. (2009). Parental attitudes on

restorative materials as factors influencing current use in pediatric dentistry. Pediatr

Dent, 31(1), 63-70.

Zinelis, S., Lambrinaki, T., Kavvadia, K., & Papagiannoulis, L. (2008). Morphological and

compositional alterations of in vivo aged prefabricated pediatric metal crowns (PMCs).

Dent Mater, 24(2), 216-220. doi: 10.1016/j.dental.2007.04.005

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Appendices

Appendix A Survey Introduction Letter

Dear Colleague,

My name is Dr. Rae Varughese and I am an MSc/Specialty student in the Department of Pediatric

Dentistry at the Faculty of Dentistry, University of Toronto.

I would like to invite you to participate in my Masters thesis research about the use of direct restorative

material choices by pediatric dentists by participating in this online questionnaire.

Your participation will help us to assess the restorative material choices for primary and permanent teeth

in the healthy, medically compromised, and developmentally delayed pediatric populations.

The survey will take approximately 20 minutes of your time to complete. There is neither cost nor

reimbursement for your participation in the study. For this study, you have been selected from the pool of

Pediatric Dentists in Canada and the United States of America and your participation is voluntary.

You are assured of complete confidentiality and anonymity in completing this survey as the ID number

will only be used to log respondents. No information that discloses personal identity will be released or

printed. Your responses will not be linked to your name in any way and will not be used in any future

publishing or presenting of the data received by this study. You are free to withdraw from the study at any

time by clicking the "exit survey" button; your withdrawal will not have any effect on your present or

future relationship with the Faculty of Dentistry, University of Toronto.

By clicking on the "yes" button, you will enter the survey and your participation in the study is assumed

to be your consent, thereby, giving permission for the contents of the survey to be used for this research.

This research has been approved by the Research Ethics Board at The University of Toronto. If you have

any questions about your rights as a participant, you may contact the ethics office at

ethics.review@utoronto.ca or (416) 946-3273. In regards to the survey itself, you can contact me at

rae.varughese@mail.utoronto.ca. Please ensure that your responses are received no later than April 30,

2013.

Thank you for your time. It's only with the generous help of people like you that our research can be

successful.

118

Sincerely,

Dr. Rae Varughese

MSc. Candidate- Pediatric Dentistry

University of Toronto, Toronto, Canada

124 Edward Street, Toronto, Canada M5G 1G6

Phone Number: 416-979-4907; E-mail: rae.varughese@mail.utoronto.ca

Co-Investigators at the Faculty of Dentistry, University of Toronto

Dr. Michael Sigal, Professor and Head, Discipline of Pediatric Dentistry and Director, Graduate Program

in Pediatric Dentistry

Dr. Paul Andrews, Assistant Professor, Department of Paediatric Dentistry

Dr. Amir Azarpazhooh, Assistant Professor, Discipline of Dental Public Health and Discipline of

Endodontics

Do you agree to participate in this study?*

Yes

No

119

Appendix B Survey

Restorative Material in the Pediatric Population - START HERE

I. Demographics

This section will collect the demographics of the participants of the survey to assess trends

in material placement and training, location, or experience.

1) What is your gender?

Male

Female

2) What year did you graduate from the Pediatric Dentistry specialty?

1950

1951

1952

1953

1954

1955

1956

1957

1958

1959

1960

1961

1962

1963

1964

120

1965

1966

1967

1968

1969

1970

1971

1972

1973

1974

1975

1976

1977

1978

1979

1980

1981

1982

1983

1984

1985

1986

1987

1988

121

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

122

3) What type of pediatric dentistry training did you receive?

Diploma/Certificate pediatric specialty training

MSc pediatric specialty training

PhD pediatric specialty training

Other:

4) In which of the following settings did you receive your pediatric dentistry training?

Hospital-based

University-based

Combined hospital and university

Other:

5) What describes your current role in pediatric dentistry?

Practicing

Retired

Pediatric dentistry resident/student

Other:

6) Which of the following best describes your current primary practice?

Private practice

Academic

Hospital-based

Publicly funded clinic (ie. dental public health/Medicaid)

Other:

123

7) In which country are you currently practicing?

Canada

United States of America

In which state are you currently practicing?

Alabama

Alaska

American Samoa

Arizona

Arkansas

California

Colorado

Connecticut

Delaware

District of Columbia

Federated States of Micronesia

Florida

Georgia

Guam

Hawaii

Idaho

Illinois

Indiana

Iowa

Kansas

124

Kentucky

Louisiana

Maine

Marshall Islands

Maryland

Massachusetts

Michigan

Minnesota

Mississippi

Missouri

Montana

Nebraska

Nevada

New Hampshire

New Jersey

New Mexico

New York

North Carolina

North Dakota

Northern Mariana Islands

Ohio

Oklahoma

Oregon

Palau

125

Pennsylvania

Puerto Rico

Rhode Island

South Carolina

South Dakota

Tennessee

Texas

Utah

Vermont

Virgin Islands

Virginia

Washington

West Virginia

Wisconsin

Wyoming

In which province/territory are you currently practicing?

Alberta

British Columbia

Manitoba

New Brunswick

Newfoundland & Labrador

Northwest Territories

Nova Scotia

Nunavut

126

Ontario

Prince Edward Island

Quebec

Saskatchewan

Yukon

8) What population do you see in your practice? Please select all that apply.*

Normal healthy

Medically compromised

Developmentally delayed/ Special needs

9) On an average day, how many patients do you perform...

0-

4

5-

9

10-

14

15-

19 20+

recall and

hygiene?

treatment?

10) What kind of payment do you accept? Please select all that apply.

Fee for service (Patient pays whole cost of treatment regardless of availability of insurance)

Private insurance (Patient pays the co-payment. The office collects insurance share)

Government funded programs (ie. Disability assistance, welfare etc.)

Other:

127

II. Restorative Material Usage

The following scenario will be used to determine material preference.

Scenario 1:

A 5 year old patient presents with buccal and occlusal caries on the mandibular right first

primary molar and mesial interproximal caries on the mandibular right second primary

molar.

Clinically, both teeth are asymptomatic, appear to be restorable, and exhibit no mobility,

sensitivity to percussion, or tenderness to palpation. Radiographically, the occlusal

radiolucency on the mandibular right first primary molar and the

interproximal radiolucency on the mandibular right second primary molar extends 0.5 mm

past the dentino-enamel junction. The patient has no furcal or periapical radiolucency and

the follicle of the permanent successor is intact. The patient’s behavior is good and does not

require sedation for treatment. The oral hygiene is fair. There are no time constraints for

treatment to be provided.

128

11) If the above patient is healthy, which material would you most prefer to use for

restoration of the carious lesion?

Amalgam Composite Compomer

Glass

ionomer

Resin-

modified

glass

ionomer

Stainless

steel

crown

Primary right

mandibular first

molar Class I

Primary right

mandibular first

molar Class V

Primary right

mandibular

second molar

Class II

12) If the above patient is medically compromised, which material would you most prefer

to use for restoration of the carious lesion?

Amalgam Composite Compomer

Glass

ionomer

Resin-

modified

glass

ionomer

Stainless

steel

crown

Primary right

mandibular

first molar

Class I

Primary right

mandibular

first molar

Class V

Primary right

mandibular

second molar

Class II

129

13) If the above patient is developmentally delayed/special needs with poor

cooperation, which material would you most prefer to use for restoration of the carious

lesion?

Amalgam Composite Compomer

Glass

ionomer

Resin-

modified

glass

ionomer

Stainless

steel

crown

Primary right

mandibular

first molar

Class I

Primary right

mandibular

first molar

Class V

Primary right

mandibular

second molar

Class II

14) Consider the same scenario as above with the modification that a mechanical pulp

exposure occurred during preparation of the primary molar.

If you perform pulp therapy treatment (pulpotomy or pulpectomy) on a primary molar,

what material would you most often use to restore the tooth?

Amalgam

Compomer

Composite

Glass ionomer

Resin modified glass ionomer

Stainless steel crown

Scenario 2:

Consider the original scenario but with a patient who is 15 years old. There are occlusal

and buccal caries on the lower right permanent first molar and mesial interproximal caries

on the lower right permanent second molar.

130

Clinically, both teeth are asymptomatic and exhibit no mobility, sensitivity to percussion,

tenderness to palpation, and appear to be restorable. Radiographically, the radiolucency

extends 0.5 mm past the dentino-enamel junction. The patient has no furcal or periapical

radiolucency. The patient’s behavior is good and does not require sedation for treatment.

The oral hygiene is fair. There are no time constraints for treatment to be provided.

15) If the above patient is healthy, which material would you most prefer to use for

restoration of the carious lesion?

Amalgam Composite Compomer

Glass

ionomer

Resin-

modified

glass

ionomer

Stainless

steel

crown

Permanent right

mandibular first

molar Class I

Permanent right

mandibular first

molar Class V

Permanent right

mandibular

second molar

Class II

16) If the above patient is medically compromised, which material would you most

prefer to use for restoration of the carious lesion?

Amalgam Composite Compomer

Glass

ionomer

Resin-

modified

glass

ionomer

Stainless

steel

crown

Permanent right

mandibular first

molar Class I

Permanent right

mandibular first

molar Class V

Permanent right

mandibular second

molar Class II

131

17) If the above patient is developmentally delayed/special needs with poor

cooperation, which material would you most prefer to use for restoration of the carious

lesion?

Amalgam Composite Compomer

Glass

ionomer

Resin-

modified

glass

ionomer

Stainless

steel

crown

Permanent right

mandibular first

molar Class I

Permanent right

mandibular first

molar Class V

Permanent right

mandibular

second molar

Class II

Scenario 3:

A 5 year old patient presents with large mesial interproximal caries on an asymptomatic

mandibular right second primary molar with buccal and lingual circumgingival

decalcification.

Clinically, it apears restorable and exhibits no mobility, sensitivity to percussion, or

tenderness to palpation. The caries extends 80% of the bucco-lingual dimension.

Radiographically, there is 25% of dentin remaining over the pulp. The patient has no

furcal or periapical radiolucency and the follicle of the permanent successor is intact. The

oral hygiene is fair. There is no time constraint for treatment to be provided.

For this large interproximal caries on a mandibular primary second molar with

circumgingival decalcification, what restorative material would you most prefer to use?

Amalgam

Compomer

Composite

Glass ionomer

Resin modified glass ionomer

Stainless steel crown

132

18) Do you use rubber dam isolation when restoring caries in the posterior dentition?

Yes

No

Sometimes

Please choose which material(s) you use rubber dam isolation when restoring the primary

or permanent dentition.

Primary Permanent

All materials

Amalgam

Compomer

Composite

Glass ionomer

Resin modified glass ionomer

Stainless steel crown

Why do you choose to use rubber dam isolation? Please select all that apply.

Poor behavior

Better view with retraction of soft tissue

Restorative material requires isolation (moisture control)

Large preparation

Other:

133

Why do you choose not to use rubber dam isolation? Please select all that apply.

Decreases time for appointments

Less traumatic for the patient

Able to prevent soft tissue from interfering without it

The material I use does not require a dry field

Better isolation without it

Other:

19) Based on scientific merit of the dental materials, identify all the factors that support

your use of that material in restoring primary or permanent molars.

If you do not use any of the materials listed, please do not provide an answer in that

column.

Amalgam Compomer Composite

Glass

ionomer

Resin-

modified

glass

ionomer

Stainless

steel

crown

Supported by

research/evidence

based

Historically safe

and reliable

Primarily taught

this material at

school

Good mechanical

properties

Fewer steps to

restore (requires

less time)

Allows for

fluoride release

(caries

prevention)

134

Lower toxicity

than other

materials

Less allergenic

Allows for a

conservative

cavity

preparation

Esthetically

pleasing

20) Based on tooth factors, identify all the factors that support your use of that material in

restoring primary or permanent molars.

If you do not use any of the materials listed, please do not provide an answer in that

column.

Amalgam Compomer

Composite

resin

Glass

ionomer

Resin-

modified

glass

ionomer

Stainless

steel

crowns

Expected lifespan of the

tooth

Subgingival preparation

margins

Gross caries requiring a

large preparation

Inability to obtain

proper isolation

After pulp treatment

(pulpectomy/pulpotomy)

Bruxism

135

21) Based on patient factors, identify all the factors that support your use of that material

in restoring primary or permanent molars.

If you do not use any of the materials listed, please do not provide an answer in that

column.

Amalgam Compomer

Composite

resin

Glass

ionomer

Resin-

modified

glass

ionomer

Stainless

steel

crowns

Patient's

age

Affordable

Based on

caries risk

assessment

Poor oral

hygiene

Poor

patient

behavior

Caregivers

insist on

using this

material

136

22) How important do you think the following factors are to the patient or caregiver?

Very

important Important

Somewhat

important

Not at

important

at all

Communication and trust between

caregivers and dentist

Patients' previous experience related to

different treatment options

Out of pocket expense to cover the cost of

treatment

Insurance coverage to cover cost of

treatment

Cost of maintaining the restoration

Complexity of restorative treatment

necessary

Number of treatment sessions required

Fear of a painful procedure

Esthetic outcome

Allows for fluoride release (caries

prevention)

Probable longevity until failure

Consequences of failure

III. Preference for Direct Restorative Material

This selection will evaluate the preference of the dental practitioner for material selection choice.

137

23) When presenting a treatment plan, how often do questions arise about restorative

materials from your patients and/or caregivers?

All of the time

Most of the time

Seldom

Never

24) Does the amount of third party reimbursement affect your choice of direct restorative

material?

Yes

No

25) In making a decision to perform restorative treatment, which role do you prefer?

I prefer to make the final decision of which treatment my patient will receive

I prefer to make the final selection of the treatment provided considering my

patients/caregiver's opinion

I prefer that the patient/caregiver and I collaboratively make the decision

I prefer that the patient/caregiver makes the final decision but seriously consider my opinion

I prefer that the patient/caregiver makes the decision

26) Do you feel pressure from patients or caregivers to provide a specific type of

treatment?

All the time

Most of the time

Sometimes

Seldom

Never

138

27) If caregivers pressure you to place a restoration that you believe is not the appropriate

restoration in this scenario, how do you deal with this situation?

Place the restoration that the parents prefer

Have the parents sign an informed consent about the restoration and its potential to fail

Continue trying to convince the caregive about the restoration you prefer

Refer the patient to a different practitioner

28) When using amalgam, how often do parents raise concerns about the mercury toxicity?

Often

Sometimes

Seldom

Never

I do not use amalgam

Most often, how do you respond when concerns arise about the safety of amalgam in

regards to mercury content?

Agree with the caregiver

Discuss the evidence about the low mercury release from amalgams

Change the treatment plan to the use of a tooth colored material

29) When using a tooth colored material, how often do caregivers raise concerns about

toxicity?

Often

Sometimes

Seldom

Never

I do not use tooth colored restorations

139

Thank you for taking our survey. Your response is very important to us.

We value your time and do not wish to inconvenience you. Your participation will assist us

in understanding how and why pediatric dentists choose certain restorative materials in

specific situations.

Please choose from the 2 options below.*

I'd like the principal investigator to contact me to discuss my concern about participating in

this study

I prefer to opt out from this study and not to receive any follow up emails about the study or

the educational material related to this topic

Please fill out your contact info

Name*

E-mail address

Phone number (office or personal)

Thank you for your participation. I am looking forward to discussing your concerns about

this survey and answering your questions.

Rae Varughese, DDS, MSc/Speciality candidate (Pediatric Dentistry)

Faculty of Dentistry, University of Toronto

124 Edward Street, Toronto, Ontario, Canada M5G 1G6

Phone: (416) 979-4907; E-mail: rae.varughese@mail.utoronto.ca