Original article

Comparison of the accuracy for three dental impression techniques

and index: An in vitro study

Erica Dorigatti de Avila DDSa,*, Luiz Antonio Borelli Barros DDS, MSc PhDb,Marcelo Antonialli Del’Acqua DDS, MSc, PhDc, Sabrina Maria Castanharo DDS, MSc, PhDa,

Francisco de Assis Mollo Jr. DDS, MSc PhDa

a Department of Dental Materials and Prosthodontics, Araraquara Dental School, Univ Estadual Paulista, Araraquara, SP, Brazilb Department of Social Odontology, Araraquara Dental School, Univ Estadual Paulista, Araraquara, SP, Brazil

c Araraquara University Center – UNIARA, Araraquara, SP, Brazil

Received 21 June 2012; received in revised form 7 May 2013; accepted 15 July 2013

Available online 26 September 2013

Abstract

Objectives: This in vitro study compared the dimensional accuracy of stone index (I) and three impression techniques: tapered impression copings

(T), squared impression copings (S) and modified squared impression copings (MS) for implant-supported prostheses.

Methods: A master cast, with four parallel implant abutment analogs and a passive framework, were fabricated. Vinyl polysiloxane impression

material was used for all impressions with two metal stock trays (open and closed tray). Four groups (I, T, S and MS) were tested (n = 5). A metallic

framework was seated on each of the casts, one abutment screw was tightened, and the gap between the analog of implant and the framework was

measured with a stereomicroscope. The groups’ measurements (80 gap values) were analyzed using software (LeicaQWin – Leica Imaging

Systems Ltd.) that received the images of a video camera coupled to a Leica stereomicroscope at 100� magnification. The results were statistically

analyzed with Kruskal–Wallis One Way ANOVA on Ranks test followed by Dunn’s Method, 0.05.

Results: The mean values of abutment/framework interface gaps were: Master Cast = 32 mm (SD 2); Group I = 45 mm (SD 3); Group T = 78 mm

(SD 25); Group S = 134 mm (SD 30); Group MS = 143 mm (SD 27). No significant difference was detected among Index and Master Cast

(P = .05).

Conclusion: Under the limitations of this study, it could be suggested that a more accurate working cast is possible using tapered impression

copings techniques and stone index.

# 2013 Japan Prosthodontic Society. Published by Elsevier Ireland. All rights reserved.

Keywords: Dental implant; Impression technique; Transfer coping; Impression material

www.elsevier.com/locate/jpor

Available online at www.sciencedirect.com

Journal of Prosthodontic Research 57 (2013) 268–274

1. Introduction

One of the main interests in implant-supported prosthesis is

the production of structures that show passive fit when connected

with multiples implants. This standard of fit is required because

of the unique quality of the implant–bone relationship [1]. The

natural tooth can move up to 100 mm within its periodontal

ligament, thus compensating for a certain degree of misfit of a

fixed partial denture, whereas an osseointegrated implant has

* Corresponding author at: Departamento de Materiais Odontologicos e

Protese, Faculdade de Odontologia de Araraquara – UNESP, Rua Humaita,

1680, Araraquara, SP 14801-903, Brazil. Tel.: +55 16 3301 6424;

fax: +55 16 3301 6406.

E-mail address: erica.fobusp@yahoo.com.br (E.D. de Avila).

1883-1958/$ – see front matter # 2013 Japan Prosthodontic Society. Published b

http://dx.doi.org/10.1016/j.jpor.2013.07.001

extremely limited movement in the range of 10 mm [2]. The lack

of intrusion movement of the implant allows the forces

introduced into an implant-supported restoration to produce a

misfit in the prosthesis. If these forces are not relieved, problems

such as screw loosening screw fracture implant fracture, and

occlusal inaccuracy may arise. Thus, this lack of flexibility of the

implants should be compensated for the correct fit between the

prosthetic components obtained by the production of an accurate

impression [3].

An accurate impression affects the accuracy of the definitive

cast, and this is essential to fabricating prosthesis with a good

fit. A successful working cast is dependent on the type of

impression material and implants transfer technique [4–6].

Dullabh and Sykes [7] reported that two of main factors that

appear to be significant for passive fit are: impression material

y Elsevier Ireland. All rights reserved.

Fig. 1. Installation of the four parallel implant analogs with Duraley resin on

master cast: (a) delineator confirming the parallelism between the implants

analogs; (b) analogs fixed with Duraley resin.

E.D. de Avila et al. / Journal of Prosthodontic Research 57 (2013) 268–274 269

and the impression technique [7]. In accordance with McCabe

and Store [8], dimensional alterations occur for various reasons:

loss of alcohol in the condensation of silicones, loss of volatile

substantiate in the polysulfide and water absorption in polyether

[8]. Vinyl polysiloxane impression material transfers the spatial

orientation of implants with equal precision when compared

with polyether materials. This occurs because the vinyl

polysiloxane presents lower modulus of elasticity and reduces

the permanent deformation caused by stress between the

impression material and the copings [9].

Implant transference techniques have a decisive influence in

the manufacturing of casts and the optimal functioning of the

prosthesis. Several studies investigated the variables affecting

the accuracy of transfer procedures in implant prosthodontics.

Among then, it is possible detach: Pick-up technique or transfer

techniques, the use of different impression materials, splinting

or surface treatment of transfer copings, the relative implant

angulations, the die material accuracy, and master cast

manufacturing [1,6,7,9,10].

There is still no consensus among researchers in regards to

the best impression techniques for implants. Thus, the aim of

the present study was analyzed the accuracy of three different

impression techniques: tapered, square and modified squared

impression coping with the master cast (control group) for

prosthesis implant-supported and determines which of the

techniques offer greater passivity with greater clinical viability.

At the same time, this study compared the results of these

techniques with the index because the index is considered to be

the best technique to reproduce the positioning of the implants.

For this, all the procedures were done using manual mixing and

conventional pouring to simulate routine clinical situations.

The null hypothesis was that there would be no significant

difference in the accuracy of casts generated with different

impression techniques.

2. Materials and methods

2.1. Obtaining the master cast

A brass mandibular edentulous cast was fabricated to

simulate a clinically relevant situation (Master Cast – control

group). Four parallel abutment analogs (Micro-Unit Abutment;

Conexao Sistema de Protese, Sao Paulo, Sao Paulo – Brazil)

were installed with Duralay resin to make their removal

possible after making the framework (Fig. 1a and b). A

framework was compost of titanium cylinders and 2 mm

diameter titanium bars (Conexao; Conexao Prosthesis Systems,

Sao Paulo, Sao Paulo – Brazil) using a laser welding technique

for allowing passive fit between the prosthetics components.

After fabrication of the framework, the Duralay resin and the

original analogs were removed and discarded. Four new

analogs were screwed to the framework with the aid of a

calibrated torque wrench (Conexao; Conexao Prothesis

Systems Ltd., Sao Paulo, Sao Paulo – Brazil) limited to

10 N cm and then embedded into the master cast holes with

epoxy resin GY 1109/943 (Huntsman Quımica Brasil Ltda, Sao

Paulo, Sao Paulo – Brasil) [10–13]. The framework was

removed from the master cast only after the polymerization of

the epoxy resin was complete. As a result, the discrepancies due

to the welding procedure were eliminated almost entirely and a

metal master cast with a passively fitting framework was

produced [10–15].

2.2. Study variables

For this study, four groups with sample size of five casts for

each group (n = 5) were evaluated:

� Index

Group I: Index group – Squared Splinted Impression

Copings. The splinting process was initiated by placing

light-polymerized composite resin (Z100; 3 M ESPE)

around the squared copings (Conexao; Conexao Prosthesis

Systems, Sao Paulo, Sao Paulo – Brazil). Performed

composite resin bars with a cross-sectional diameter of

approximately 3 mm were fabricated by the injection of

composite resin into a drinking straw [17]. Appropriate

Fig. 2. Splinted squared impression copings for index technique.

Fig. 3. Tapered impression copings.

Fig. 4. Modified squared impression copings.

Fig. 5. Squared impression copings.

E.D. de Avila et al. / Journal of Prosthodontic Research 57 (2013) 268–274270

lengths of the resin bar were sectioned with a cutting disk

to bridge the spaces between the adjacent impression

copings. The ends of the resin bar were luted to the

impression copings with composite resin (Fig. 2).

� Transfer technique

Group T: Tapered impression coping (Fig. 3)

� Pick-up techniques

Group S: Squared impression copings (Fig. 4)

Group MS: Modified squared impression copings – Pick-

up technique – Squared impression copings with 2 mm

prolongations created with autopolymerizing acrylic resin

(Duralay; Reliance Dental Mfg, Worth, IL) (Fig. 5).

Metal stock trays were used to facilitate and simplify the

impression techniques [16]. The fitting surfaces of all

components were cleaned with isopropyl alcohol before each

impression [17]. All squared impression copings (Micro-Unit

Abutment, Conexao Sistema de Protese, Sao Paulo, Sao Paulo –

Brazil) were adapted to the abutment analogs on the master cast

using 10 N cm torque [18]. Correct seating of the impression

copings was verified visually throughout the impression and

pouring procedures.

2.3. Impression

The impressions were made in a temperature-controlled

environment. Vinyl polysiloxane impression material (Elite

HD+ putty/light body normal setting, Zhermack, Badia

Polesine, Italy) was used according to the manufacturer’s

instructions.

Each impression was produced with equal quantities of

impression material. The impression material was allowed to

set for 10 min after the mixing was started. The manufacturer’s

setting time was doubled to compensate for a delayed

polymerization reaction at temperature environment rather

than at mouth temperature [17,20,21]. For transfer technique,

the impression/matrix set was separated (Fig. 6).

Tapered copings were unscrewed of the analogs and placed

in the mold for all impression.

For Pick-up techniques, after impression material poly-

merization, the impression copings were unscrewed and the

tray was separated from the master cast (Fig. 7). In this case,

when the impression/matrix set are separated, the transfer are

close to the impression.

The squared impression copings and modified squared

impression copings were secured onto the analogs with guide

screws (Fig. 8).

2.4. Confection of stone casts

With the index group, squared splinted impression copings

were unscrewed from the master cast and screwed to the

abutment analogs. A rectangular box for pouring was made with

Fig. 6. Transfer technique.

Fig. 7. Pick-up technique.

Fig. 8. Squared impression copings positioned on the analogs with guide

screws.

Fig. 9. Index – a rectangular box was made with type IV dental stone.

E.D. de Avila et al. / Journal of Prosthodontic Research 57 (2013) 268–274 271

condensation silicone and poured with type IV dental stone

(Fig. 9). The analogs were seated into the stone matrix to,

approximately, half their length. For the Pick-up techniques, four

windows were created in the metal stock tray to expose coping

screws. A box for pouring the impression with dental stone was

made with condensation silicone (Zetaplus/Oranwash; Zermack,

Badia Polesine, Rovigo, Italy). This matrix was used for all the

impressions, allowing the reproduction of the tray position and

standardization of the format of the casts and of the amount of

dental stone. The conventional pouring techniques were used

since these techniques are easier and faster. Two hours after the

impressions; the dental stone type IV (Durone IV – Dentsply

Industria e Comercio Ltda., Petropolis, Rio de Janeiro, Brasil)

was mechanically handled to simulate a routine clinical situation.

All mixes were vibrated into boxed impressions and before and

during the pouring [9]. The 20 casts obtained were stored for two

weeks before measurement [17–23]. The four implant analogs in

the master cast were denoted sequentially A through D from left

to right.

2.5. Registration of misfits vertical (adaptation cervical)

The standard framework was seated on each cast and a

titanium screw was tightened in analog A to 10 N cm using a

torque driver, while measurements of abutment-framework

interface gaps were made in analogs C and D.

This process was repeated for analog D, and the measure-

ments of analogs A and B were noted. These measurements

were analyzed using software (Leica Imaging System, Cam-

bridge, England) that received the image from a video camera

(JVC, 0.5-in. CCD, model TK-C1380, Tokyo, Japan) coupled

to a Leica stereomicroscope (Leica Microsystems, Wetzlar,

Germany) at 100� magnification. Demarcations were made in

the relative center of each abutment between the metallic

structure and the analog implants to standardize the captured

image. For each picture taken, the lineal reading of gap was

carried through in three areas. The arithmetic mean of these

three values determined the value of the gap. The mean gap

value for the master cast was calculated as the average of five

consecutive measurements (20 gap values), and the framework

was screwed before each measurement. The same person

performed all procedures [10,24,16].

2.6. Statistical analysis

All measurements were registers by same blind examiner

calibrated. One person analyzed the same images in two

different occasions to confirm the reliability the calibration of

Table 1

Kruskal–Wallis One Way analysis of variance on ranks.

Group Mean Median 25% 75%

Master Cast 31.63 28.865 20.39 42.87

(I) Index 45.25 43.12 30.625 58.555

(T) Tapered 78.34 71.82 54 99.375

(S) Squared 133.78 129.795 104.31 157.335

(ms) Modified squared 143.15 145.775 117.34 174.045

* H = 72.346 with 4 degrees of freedom. (P = < 0.001).

Table 2

Comparison of all transfer techniques vs. master cast (Dunn’s method).

Comparison Diff. of ranks Q P < 0.05

Index vs. master cast 11.8 1.286 No

Tapered vs. master cast 32.2 3.51 Yes

Squared vs. master cast 58.55 6.382 Yes

Modified squared vs. master cast 62.2 6.78 Yes

E.D. de Avila et al. / Journal of Prosthodontic Research 57 (2013) 268–274272

the examiner, with confidence interval of 95% in two different

occasions. With the aid of SigmaStat version 3.11 (Systat,

Evanston, IL), an appropriate statistical test, for small samples,

was applied. Because it is a non-normal distribution with

unequal variances, a One-Way analysis of variance the

Kruskal–Wallis One Way ANOVA was used. Values of

P < .05 were judged to be significant. The results showed that

there were significant differences among groups. For this

reason, Dunn’s Method posttest was used to perform multiple

comparisons between groups.

3. Results

Four groups with five casts each were formed. The mean

values of abutment/framework interface gaps were: Master

Cast = 32 mm (SD 2); Group I = 45 mm (SD 3); Group

T = 78 mm (SD 25); Group S = 134 mm (SD 30); Group

MS = 143 mm (SD 27). There were significant differences

among groups. Table 1 shows all comparisons among the

groups. The index group was the one that most approached the

Master Cast results (P = .05). Among the impression techni-

ques the Group T presented better results. In contrast, the

Groups S and MS presented the highest gaps determined by the

distance between the framework and the analog. The

differences between S and MS Groups did not produce

significant difference. Table 2 shows, which transfer techni-

ques, are statistically different in comparison with Master Cast.

The results show that only the gap value of Index Group no

present difference in relation to Master Cast.

4. Discussion

The master cast reproduces the intraoral position of the

implants surrounding hard and soft tissues as accurately as

possible, to allow for the fabrication of passively fitting

prostheses and, consequently, eliminate the strain on the

supporting components and around the bone.

If a clinically passive fit is not achieved and the metal

supporting structure is intraorally unstable, the metal frame-

work is usually sectioned, repositioned, and soldered. But this

involves more time and produces a weaker and metallurgically

more complex prosthetic framework [4,21]. A passive fit occurs

when all the surfaces, of the implant and prosthesis, are aligned

without the application of force and when the gap formed

between the metallic framework and implants are within the

limits established by science (111 mm) [25]. However, a gap of

32 mm was still observed between the framework and implant

analogs. This gap is equivalent to the distance between the

analog D and the framework, result of screw tightness on the

set: analog A and framework [10].

A perfect fit occurs when all the matching surfaces of the

implant and prosthesis are in alignment and in contact without

the application of force [5]. In order to identify a passive fit, the

master cast used in this study was fabricated using a previously

completed metal framework.

The scientific literature provides two impression techniques,

which are pick-up and transfer techniques

[1,3,7,10,13,15,17,27,28]. The second technique is performed

with tapered impression copings associated with tray closed.

On the other hand, in the pick-up technique, the square

impression copings are unscrewed of the implant after the

setting of the impression material and removed from the mold,

using a tray opened. The type of tray is directly related with the

dental impression technique used [26]. An ideal impression

technique would require minimal time, be useful, inexpensive,

and comfortable for the patient and, of course, provided more

accurate results [26]. While some authors reported better results

with the pick-up technique [27,28], Humphries and colleagues

found that the transfer technique was more accurate, required

less working time, and was easier for the operator and also more

comfortable for the patient [3]. The feasibility of the transfer

technique enables indication for patients with limited mouth

opening, and patients with an exaggerated gag reflex due the

ease and the speed of removal [5]. In 2009, Rashidan et al. [29]

compared the accuracy of two different impression techniques

with two different coping shapes and showed that was not

statistical significant difference in whole dimensions between

pick-up and transfer impressions techniques.

These results are inconsistent with several other investiga-

tions [22,27], and may be related to the use of different

materials for impression, casting, different prosthetic compo-

nents, mixing time, and type of tooling. However, in the present

study, tapered coping techniques presented gap values higher

than those observed with the index, but lower than other

techniques (squared and modified squared). Thus, the clinician

should choose the technique that requires less time (Group T),

since it is much easier to use. The null hypothesis that the

accuracy of casts would not be affected by the impression

technique was rejected. Significant differences were detected

among T, S and MS groups and Master Cast.

Despite some author’s affirmations that the splinted square

coping technique offers more accurate results [1,11,13,15,30],

others report that the splinted square coping technique showed

no benefit over the square coping technique [17,11]. The aim of

E.D. de Avila et al. / Journal of Prosthodontic Research 57 (2013) 268–274 273

splint the square coping is to stabilize the copings during the

impression to minimize the rotation movement during the

setting time of the impression material. However, this technique

emanates a long time, it is not easy and it is no comfortable for

patient. At the same time, some authors affirm that the choice of

the impression technique must be accompany the impression

material and impression tray specific for that technique.

Considering the clinic practical unviability, this study did not

cite the splinted square coping techniques.

The inaccuracy observed in tapered coping technique may

be correlated with the distortion of the impression material

during removal. Daoudi et al. [31] demonstrated that a large

variation was reported in the anteroposterior and mesiodistal

positions of the coping in the repositioning technique [31].

Similarly, Liou et al. [32] studied the accuracy of repositioning

tapered transfer copings within the impressions elastomeric and

noted that the part cannot be repositioned accurately in all

impressions [32]. Carr noted that the inaccuracy of the transfer

techniques might arise from the apparent deformation caused

by a stiff impression material such as polyether. Thus, a more

elastic impression material could reduce the deformation of the

impression. In this case in question, for impression of the

analogs, the 1-step putty-wash technique using vinyl poly-

siloxane impression material was chosen because of its

convenience, common clinical usage and because the literature

shows more accurate results [26]. Other technique, also

commonly used, is with 2-step putty-wash technique. An

advantage of the two-step impression technique is that the

impression of the teeth can be captured with the wash material.

While the disadvantages are distortions, extra chair side time,

and extra material needed [33].

The squared and modified squared coping technique groups

present the highest gap values, and show the deficiencies of

these types of impressions. In relation to square coping

technique, the results could be justified due to a possible

rotating movement during the impression. These results

contradict some scientific literature that presents satisfactory

results with the use of the square coping techniques [27,28].

However, due to the fact that the casting was done using the

conventional method (without the use of the latex tube) [10],

the expansion of the plaster could have caused distortions in the

impression and the formation of gaps. For this reason, it was

created prolongation with acrylic resin on squared impression

copings to simulate a guide screws. Thus, this extension could

avoid the rotating movement of the square copings during the

impression. However, the results showed the opposite. The

modified squared coping technique group presented a gap of

145,77 mm, determined by the arithmetic mean of three values

referents to the distance between the framework and the analog

determined the value of the gap. The minors gaps observed in

Index Group could be explained by the absence of the

impression material for this technique. For the Index Group, a

small amount of dental stone is employed in the pouring

procedure and this fact could be minimizes the setting

expansion. According to Del’Acqua et al. [10], the index

technique (Group I = 45 mm) was the best technique for

production of implant-supported and fixed restorations with

dimensional accuracy. The clinical advantages in splints

squared copings with light-polymerized composite resin are

minimize problems related to resin polymerization contraction

and avoid this multi-step, time-consuming procedure (time

required for acrylic resin polymerization and the additional step

of sectioning and rejoining the acrylic resin splint). Therefore,

there is improved efficiency, a reduction of chair time and

greater transfer precision due to the splinting stability. If the

final prosthesis is fitted on the index, then, a clinician should

trust that it would most likely fit a patient’s mouth [34]. This

would be advantageous, since passive adaptation of the implant

abutment to the framework is often difficult to achieve and to

interpret in a clinical setting [35].

Further studies evaluating implant impression techniques

simulating partially edentulous casts are necessary. In addition,

other types of impression materials should be also evaluated.

Considering that this study is an in vitro study, and it is

impossible to simulate all clinical conditions, the techniques

evaluated are expected to perform similarly in the oral

environment.

5. Conclusion

Under the limitations of this study, it could be suggested that

a more accurate cast work could be performed using both

techniques: tapered coping technique and the index technique.

Tapered coping technique was not only considered to be

technically easier to work with but also numerically better.

Squared coping and modified squared coping techniques did

not present any clinical advantage and did not improve the

dimensional accuracy of the die stones to interpret a clinical

situation.

Conflict of interest

The authors declare that they have no conflict of interest.

Acknowledgement

The authors acknowledge with sincere thanks the Mrs. Kim

Kubitza for correcting the English language this article.

References

[1] Assif D, Nissan J, Varsano I, Singer A. Accuracy of implant impression

splinted techniques: effect of splinting material. Int J Oral Maxillofac

Implants 1999;14:885–8.

[2] Rudd KD, O’Leary TJ, Stumf AJ. Horizontal tooth mobility in carefully

screened subjects. Periodontics 1964;2:65–8.

[3] Humphries RM, Yaman P, Bloem TJ. The accuracy of implant master casts

constructed from transfer impressions. Int J Oral Maxillofac Implants

1990;5:331–6.

[4] Sahin S, C ehreli MC. The significance of passive framework fit in implant

prosthodontics: current status. Implant Dent 2001;10:85–92.

[5] Chee W, Jivraj S. Impression techniques for implant dentistry. Br Dent J

2006;201:429–32.

[6] Wee AG. Comparison of impression materials for direct multi-implant

impressions. J Prosthet Dent 2000;83:323–31.

[7] Dullabh HD, Sykes LM. The accuracy of three impression transfer

techniques for implant supported prostheses. S Afr Dent J

2008;63:458–65.

E.D. de Avila et al. / Journal of Prosthodontic Research 57 (2013) 268–274274

[8] McCabe JF, Storer R. Elastomeric impression material: the measurement

of some properties relevant to clinical practice. Br Dent J 1980;149:73–9.

[9] Stefan H, Blatz MB, Bergler M, Goellner M, Wichmann M. Influence of

impression material and time on the 3-dimensional accuracy of implant

impressions. Quintessence Int 2007;38:67–73.

[10] Del’Acqua MA, Arioli-Filho JN, Compagnoni MA, Mollo Jr FA. Accu-

racy of impression and pouring techniques for an implant-supported

prosthesis. Int J Oral Maxillofac Implants 2008;23:226–36.

[11] Assif D, Marshak B, Schmidt A. Accuracy of implant impression tech-

niques. Int J Oral Maxillofac Implants 1996;11:216–22.

[12] De La Cruz JE, Funkenbusch PD, Ercoli C, Moss ME, Graser GN, Tallents

RH. Verification jig for implant-supported prostheses: a comparison of

standard impressions with verification jigs made of different materials. J

Prosthet Dent 2002;88:329–36.

[13] Naconecy MM, Teixeira ER, Shinkai RS, Frasca LC, Cervieri A. Evalua-

tion of the accuracy of 3 transfer techniques for implant-supported

prostheses with multiple abutments. Int J Oral Maxillofac Implants

2004;19:192–8.

[14] Assif D, Fenton A, Zarb G, Schmitt A. Comparative accuracy of implant

impression procedures. Int J Periodontics Restorative Dent 1992;12:112–21.

[15] Vigolo P, Majzoub Z, Cordioli G. Evaluation of the accuracy of three

techniques used for multiple implants abutment impressions. J Prosthet

Dent 2003;89:186–92.

[16] Del’acqua MA, de Avila ED, Amaral AL, Pinelli LA, de Assis Mollo Jr F.

Comparison of the accuracy of plastic and metal stock trays for implant

impressions. Int J Oral Maxillofac Implants 2012;27:544–50.

[17] Burawi G, Houston F, Byrne D, Claffey N. A comparison of the dimen-

sional accuracy of the splinted and unsplinted impression techniques for

the Bone-Lock implants system. J Prosthet Dent 1997;77:68–75.

[18] Ivanhoe JR, Adrian ED, Krantz WA, Edge MJ. An impression technique

for osseointegrated implants. J Prosthet Dent 1991;66:410–1.

[19] Dumbrigue HB, Gurun DC, Javid NS. Prefabricated acrylic resin bars for

splinting implant impression copings. J Prosthet Dent 2000;84:108–10.

[20] Nissan J, Laufer B-Z, Brosh T, Assif D. Accuracy of three polyvinyl siloxane

putty-wash impression techniques. J Prosthet Dent 2000;83:161–5.

[21] Lorenzoni M, Pertl C, Penkner K, Polansky R, Sedaj B, Wegscheider WA.

Comparison of the transfer precision of three different impression materi-

als in combination with transfer caps for the Frialit1-2 systems. J Oral

Rehabil 2000;27:629–38.

[22] Inturregui JA, Aquilino SA, Ryther JS, Lund PS. Evaluation of three

impression techniques for osseointegrated oral implants. J Prosthet Dent

1993;69:503–9.

[23] Nissan J, Gross M, Ormianer Z, Barnea E, Assif D. Heat transfer of

impression plasters to an implant–bone interface. Implant Dent

2006;15:83–8.

[24] Del Acqua MA, Chavez AM, Castanharo SM, Compagnoni MA, Mollo

Fde Jr A. The effect of splint material rigidity in implant impression

techniques. Int J Oral Maxillofac Implants 2010;25:1153–8.

[25] Jemt T, Book K. Prosthesis misfit and marginal bone loss in edentulous

implant patients. Int J Oral Maxillofac Implants 1996;11:620–5.

[26] Wenz HJ, Hertrampf K. Accuracy of impressions and casts using different

implant impression techniques in a multi-implant system with an internal

hex connection. Int J Oral Maxillofac Implants 2008;23:39–47.

[27] Phillips KM, Nicholls JI, Ma T, Rubenstein J. The accuracy of three

implant impression techniques: a three-dimensional analysis. Int J Oral

Maxillofac Implants 1994;9:533–40.

[28] Carr AB. Comparison of impression techniques for a five implant man-

dibular model. Int J Oral Maxillofac Implants 1991;6:448–55.

[29] Rashidan N, Alikhasi M, Samadizadeh S, Beyabanaki E, Kharazifard MJ.

Accuracy of implant impressions with different impression coping types

and shapes. Clin Implant Dent Relat Res 2009;1–8.

[30] Avila ED, Moraes FD, Castanharo SM, Del Acqua MA, Mollo Jr FA.

Effect of splinting in accuracy of two implant impression techniques. J

Oral Implantol 2012. October 26 [Epub ahead of print].

[31] Daoudi MF, Setchell DJ, Searson LJ. A laboratory investigation of the

accuracy of two impression techniques for single-tooth implants. Int J

Prosthodont 2001;14:152–8.

[32] Liou AD, Nicholls JI, Youdelis RA, Brudvik JS. Accuracy of replacing

three tapered transfer impression copping in two elastomeric impression

materials. Int J Prosthodont 1993;6:377–83.

[33] Hung SH, Purk JH, Tira DE, Eick JD. Accuracy of one-step putty wash

addition silicone impression technique. J Prosthet Dent 1992;67:

583–9.

[34] Hussaini S, Wong T. One clinical visit for a multiple implant restoration

master cast fabrication. J Prosthet Dent 1997;78:550–3.

[35] Waskewicz GA, Ostrowski JS, Parks VJ. Photoelastic analysis of stress

distribution transmitted from a fixed prosthesis attached to osseointegrated

implants. Int J Oral Maxillofac Implants 1994;9:405–11.