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INFLUNCIA DOS AGENTES DESSENSIBILIZANTES SOBRE A RESISTNCIA

AO MICRO-CISALHAMENTO DE SISTEMAS ADESIVOS PARA DENTINA

INTRODUCTION

Post-operative sensitivity is commonly found in vital

teeth after the use of adhesive systems that require

acid etching. Some clinical studies have revealed thepresence of post-operative discomfort in up to 14%

subjects after the restorative procedure1,2.

Dentin sensitivity (DS) is a great challenge to the

dentist3,4. It is a painful clinical condition that affects

40 million Americans who present some kind of dis-

comfort at any time during their life5. Murray6

(1994) reported that the mean prevalence of sensi-

tive teeth is 14.8% in six countries around the world.

Exposed dentin can be sensitive to mechanical, ther-

mal or osmotic stimuli. The non-carious etiologies

for DS are abrasion, abfraction or erosion lesions,

gingival recession or periodontal therapy7. Abrasion

is the most common loss of dental structure, caused

by brushing techniques and the use of abrasive tooth-

paste. Abfraction is the loss of current dental struc-

tures, caused by traumatic occlusion loads. Erosion

is the chemical dissolution of the dental structure,

frequently caused by gastric acids, diet or the dental

environment. DS can also be a post-operative com-

plication associated with dental procedures.

Morphological and physiological studies suggest

that dentin hypersensitivity results from exposure

of dentin surfaces to the oral environment8,9. Nowa-

days, the most accepted theory to explain DS is the

hydrodynamic theory of Brnnstrm10 (1992), who

suggested that dentin sensitivity originates after the

INFLUENCE OF DESENSITIZING AGENTS ON THE MICROSHEARBOND STRENGTH OF ADHESIVE SYSTEMS TO DENTIN

Fernando A. Maeda1, Ana P.A. Guedes2, Anderson Catelan2, Sabrina Pavan1,Andr L.F. Briso2, Renato H. Sundfeld2, Paulo H. dos Santos1

1 Department of Dental Materials and Prosthodontics.2 Department of Restorative Dentistry. So Paulo State University

Araatuba School of Dentistry, UNESP, Brazil.

Vol. 22 N 1 / 2009 / 41-45 ISSN 0326-4815 Acta Odontol. Latinoam. 2009

41

ABSTRACT

The aim of this study was to evaluate the effect of desensitiz-

ing agents on the micro-shear bond strength of adhesive

systems to dentin. Forty bovine teeth were divided into 8

groups (n=5): G1 - Single Bond (SB); G2 - G.H.F. + SB; G3 -

Desensibilize + SB; G4 - Dessensiv + SB; G5 - Single Bond 2

(SB2); G6 - G.H.F. + SB2; G7 - Desensibilize + SB2; G8 -Dessensiv + SB2. In all of the groups, the desensitizing agents

were applied after phosphoric acid etching and before the

dentin adhesive application. Z250 composite resin tubes were

bonded on the treated surface. After 24 hours, the teeth were

tested in a universal machine. Data were submitted to ANOVA

and Tukeys test (5%). The results showed that the groups

where Desensibilize and Dessensiv were applied exhibited

smaller bond strength values.

Key words: desensitizing agents, dentinal adhesive, micro-

shear bond strength.

RESUMO

O objetivo deste estudo foi avaliar o efeito dos agentes

dessensibilizantes sobre a resistncia de micro-cisalhamento

de sistemas adesivos dentina. Quarenta dentes bovinosforam divididos em 8 grupos (n = 5): G1 - Single Bond (SB);

G2 - GHF + SB; G3 - Desensibilize + SB; G4 - Dessensiv +

SB; G5 - Single Bond 2 (SB2); G6 - GHF + SB2; G7 - Desen-

sibilize + SB2; G8 - Dessensiv + SB2. Em todos os grupos,

os agentes dessensibilizantes foram aplicados aps o condi-

cionamento da dentina com cido fosfrico e antes da

aplicao adesiva. A resina composta Z250 foi colocada

sobre a superfcie tratada. Aps 24 horas, os dentes foram

submetidos ao teste em uma mquina universal. Os dados

foram submetidos ANOVA e teste de Tukey (5%). Os resul-tados mostraram que os grupos onde foram aplicados

Desensibilize e Dessensiv exibiram menores valores de

resistncia ao micro-cisalhamento.

Palavras chave: agentes dessensibilizantes, adesivos denti-

nrios, micro-cisalhamento.


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Table 1: Materials used in this study

Acta Odontol. Latinoam. 2009 ISSN 0326-4815 Vol. 22 N 1 / 2009 / 41-45

42 Fernando A. Maeda, Ana P. A. Guedes, Anderson Catelan et al.

displacement of the tubular fluid, stimulating a

nerve receptor, which results in the transmission of

the stimuli10

.Based on this hypothesis, desensitizing agents have

been used for treatment of DS. These agents have

different mechanisms of action, but generally seek to

obliterate the dentin tubules, precipitate proteins that

constitute Tomes process (silver nitrate, zinc chlo-

ride), inhibit the formation and deposition of crystals

in the mouth and interior of the dentin tubules (fluo-

ride compounds, strontium chloride, potassium

oxalate), or cover the dentin by impregnation of the

tubules. Finally, some agents employ dentin bonding

agents with and without resin-based composite11,12.Few studies evaluating the effect of desensitizing

on micro-shear bond strength of bonding agents to

dentin have been reported in the literature. Thus,

this study evaluated the influence of some desensi-

tizing agents on the bond strength of adhesive sys-

tems to dentin.

MATERIALS AND METHODS

The compositions, manufacturers and batch num-

bers of the materials used in this study are listed in

Table 1.

Tooth preparation

Forty bovine incisors were stored in distilled water

at room temperature for 1 month until the beginningof the study. The teeth were cleaned and polished

using pumice and water with a brush in a low-speed

handpiece. The roots were sectioned and the crowns

embedded in acrylic resin (Clssico, Dental Prod-

ucts, So Paulo, SP, Brazil) in PVC tubes, with the

buccal surface 1 mm above the edge of the tube.

The buccal surface of each tooth was ground with

wet 180-, 400-, and 600-grit silicon carbide abra-

sive paper in a horizontal grinder (APL-4, Arotec,

So Paulo, SP, Brazil) until a dentin surface was

exposed. The exposed dentin surface was thenexamined using a 63X stereoscopic loupe (Carl

Zeiss, Jena, Germany) for complete removal of

enamel. Teeth were randomly divided into 8 groups

(n=5), according to the bonding procedures.

Bonding procedures

All the samples were etched with 37% phosphoric

acid for 15 seconds and rinsed with water for 20

seconds. The surfaces were gently dried with

absorbing paper and submitted to the procedure

described below (Table 2).

Materials

Adper Single Bond

Adper Single Bond 2

Z-250

Tooth Conditioner Gel

Desensibilize

Dessensiv

G.H.F.

Composition

Bis-GMA, HEMA, ethanol, water

Bis-GMA, HEMA, dymetacrylate,

ethanol, water,

Bis-GMA, UDMA, Bis-EMA,

Zircon/silica

37% Phosphoric acid

Strontium chloride, potassium

nitrate, water, thickener and

humectant

Potassium oxalate, potassiumfluoride, potassium nitrate,

hydroxyethylcellulose,

phosphoric acid and water

Glutaraldehyde, HEMA

Manufacturer

3M ESPE, St. Paul, MN, USA

3M ESPE, Irvine, CA, USA

3M ESPE, St. Paul, MN, USA

Dentsply Latin America,

Petrpolis, RJ, Brazil

FGM Produtos Odontolgicos,

Joinville, SC, Brazil

S.S.White, Rio de Janeiro, RJ,Brazil

Biodinmica, Ibipor, PR, Brazil

Batch #

1GA

HYK

5RF

242437

02 Mar 05

003

479/05


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Z250 composite resin cylinders

were prepared inserting the

composite in Tygon-Micro-

bone (TGY-030, Small Parts

Inc.) tubes, 0.7 mm in internal

diameter and 0.7 mm in height,

and photo-cured for 20 secondsusing Ultralux (Dabi Atlanti,

Ribeiro Preto, Brazil) with

500 mW/cm2, and the tip posi-

tioned close to the Tygon

microtubes. After the proce-

dure, the tubes were removed

carefully. Three cylinders of

Z250 composite resin were bonded with the dentin

adhesive in each prepared tooth in all of the groups.

All teeth were stored in distilled water for 24 hours

at 37C.

Microshear bond test

The samples were submitted to micro-shear bond

testing in a universal machine EMIC (model DL

3000) operated at 0.5 mm/minute. For this proce-

dure, an orthodontic wire - 0.3 mm in diameter and

5 mm in length - was used to form a loop involving

the composite cylinder in the bonded area, induc-

ing a tensile effort which generated a shear move-

ment. The micro-shear bond strength was calculatedby the following formula:

R = F/A where: R is the micro-shear bond strength;

F is the applied force; and A is the bonded area.

The micro-shear bond strength values were submit-

ted to two-way ANOVA and the

averages compared by Tukeys

test (5%).

RESULTS

For Single Bond dentin adhe-

sive, the control (23.79 4.58MPa) and G.H.F. (20.68 3.82

MPa) groups exhibited the high-

est values of micro-shear bond

strength, with no statistical dif-

ference between them (p>0.05).

Similarly, these groups present-

ed the highest values when Sin-

gle Bond 2 was used as dentin

adhesive (22.51 2.13 MPa;

20.39 4.28 MPa, respectively).

The application of the agents,

Dessensibilize and Dessensiv, decreased the micro-

shear bond strength for Single Bond (16.04 2.91

MPa; 14.85 2.11 MPa) and Single Bond 2 (15.02

0.75 MPa; 15.97 2.51 MPa) (p0.05).

DISCUSSION

The choice of dentin adhesive should consider both

its final adhesion to dentine and its capacity to resist

the stress generated by the polymerization of therestoring material13, in order to avoid the invasion

of bacteria and post-operative sensitivity.

Dentin desensitizing agents have been used before

the application of dentin adhesives that require acid


Influence of desensitizing agents on the microshear... 43

Table 2: Bonding procedures in the tested groups

Group

G1

G2

G3

G4

G5

G6

G7

G8

Desensitizing agent

None

G.H.F. (30s)

Desensibilize (10 min)

Dessensiv (30s)

None

G.H.F. (30s)

Desensibilize (10 min)

Dessensiv (30s)

Wash

None

rinsed in water (60s)



None




Adhesive

Single Bond

Single Bond

Single Bond

Single Bond

Single Bond 2

Single Bond 2

Single Bond 2

Single Bond 2

Fig. 1: Micro-shear bond strength, comparing the groups for both Single Bond and

Single Bond 2 dentin adhesives. Bars with different letters are statistically different

(p


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etching, to prevent dentin sensitivity. According to

Brannstrms Hydrodynamic theory10 (1992),

dentin sensitivity originates from the dentinal fluid

displacement due to dentin exposure. Within this

context, desensitizing agents act as a type of plo-

sive, obliterating the dental tubules.

G.H.F. is a desensitizing agent, containing glu-

taraldehyde and HEMA. Glutaraldehyde is believed

to provoke dentinal fluid protein coagulation, and

coagulation is facilitated by HEMA that is highlywater soluble.14,15

Some researchers have reported the clinical efficien-

cy of glutaraldehyde and HEMA containing products

in the treatment of dentin hypersensitivity16,17. Prior

application of G.H.F. did not show any statistical dif-

ference with the control groups for both the adhe-

sives under study (Figure 1). These results agree with

those obtained by Cobb18 et al. (1997), Reinhardt19 et

al. (1995) and Soeno20 et al. (2001), who used a prod-

uct containing glutaraldehyde and HEMA, that did

not interfere in the bonding of resinous cements tothe dentine. In our study, however, the product was

applied before acid conditioning.

The efficiency of adhesion is related to factors such

as viscosity and degree of conversion of the adhesive

and the collapse of the collagen fibril mesh that may

hinder the penetration of the monomers into the inter-

fibril spaces and the complete involvement of the col-

lagen fibrils exposed for conditioning etching21,22.

The groups treated with Desensibilize demonstrated

a reduction in bond strength that was statistically sig-

nificant in relation to the control groups for both

adhesives under study. Desensi-

bilize contains strontium chlo-

ride in its composition; the

decrease in bond strength

observed with this material may

be due to the deposition of crys-

tals, formed by the change in thecalcium of the dentine as a

result of its interaction with

strontium. Seara23 et al. (2002)

reported that the formation of

acid-resistant crystals is caused

by the reaction between stron-

tium chloride and dentin and

could inhibit, chemically and/or

physically, the permeability of

dentin and mechanical retention

among the resinous monomers

in the dentin. Permeability would be one of the most

important factors in incomplete infiltration of the

adhesive, decreasing the bond strength to dentin24. In

some studies, the use of desensitizing agents reduced

dentin permeability by 80%25-27.

The application of Dessensiv caused a decrease in

the micro-shear bond strength for both adhesives

when compared with the control groups (Fig. 1).

This effect could be attributed to the presence of

potassium oxalate, which reacts with the dentin,forming calcium oxalate crystals. This result is in

keeping with Al Qahtani28 et al. (2003) and Have-

man & Charlton29 (1994), who obtained lower val-

ues when desensitizing materials with potassium

oxalate in their composition were used.

The compositions of Single Bond and Single Bond

2 dentin adhesives are similar, with the latter includ-

ing 10% w/w spherical 5 nm diameter silica parti-

cles. It is suggested by the manufacturer that the

nanoparticles may create a more uniform hybrid

layer, and contribute to increasing the bond strengthto dentin. However, in our study, no difference in

the micro-shear bond strength was observed, even

in the treated groups (Fig. 2).

CONCLUSION

The results obtained in this study suggest that

G.H.F. does not interfere in the micro-shear bond

strength of dentin adhesives to dentin; however, the

desensitizing agents, Desensibilize and Dessensiv,

reduced the bond strength when Single Bond and

Single Bond 2 were used.

44 Fernando A. Maeda, Ana P. A. Guedes, Anderson Catelan et al.

Acta Odontol. Latinoam. 2009 ISSN 0326-4815 Vol. 22 N 1 / 2009 / 41-45

Fig. 2: Micro-shear bond strength, comparing the Single Bond and Single Bond 2

dentin adhesives for all the treated groups. Bars with different letters are statistically

different (p


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Influence of desensitizing agents on the microshear... 45


CORRESPONDENCE

Dr. Paulo Henrique dos Santos

Department of Dental Materials and Prosthodontics

Araatuba School of Dentistry - UNESP

Rua Jos Bonifcio, 1193 Araatuba - SP. Brazil

Zip code: 16015-050

[email protected]

acta oodntol latin 09 adesao dessensi

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