Australian Dental Journal

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Australian Dental Journal The official journal of the Australian Dental Association SCIENTIFIC ARTICLE Australian Dental Journal 2012; 57: 184 189 doi: 10.1111/j.1834-7819.2012.01685.

Dentistry, Istanbul University, Istanbul, Turkey.

1 Australian Dental Journal The official journal of the Australian Dental Association SCIENTIFIC ARTICLE Australian Dental Journal 2012; 57: doi: /j x A comparative analysis of the accuracy of different direct impression techniques for multiple implants D Öngül,* B Gökçen-Röhlig,* B S ermet,* H Keskin* *Department of Prosthodontics, Faculty of Dentistry, Istanbul University, Istanbul, Turkey. ABSTRACT Background: The aim of this study was to compare the accuracy of different direct implant impression techniques for edentulous arches with multiple implants. Methods: Five experimental groups (n = 5) were assembled. Experimental models were created by a direct splinted technique (EG2 to EG5) and a non-splinted technique (EG1). In EG2 and EG3 synocta impression copings were splinted with an acrylic resin bar, and in EG4 and EG5 with a light-curing composite resin bar. In EG3 and EG5 the resin bars were sectioned, while the other experimental groups were not. Three-dimensional discrepancies were measured by a computerized coordinate measuring machine. Distortion values among the groups were analysed using one-way repeated measures ANOVA. The post hoc Tukey s test was then performed for multiple comparisons. Results: The highest accuracy was obtained in EG2 (mean deviation: lm). The acrylic bars demonstrated less deviation (12.70 lm and lm) from the master model than the light-curing composite resin groups and the nonsplinted group (41.09 lm). The post hoc Tukey s test showed no significant difference among the groups when the effect of splint design on accuracy was investigated. Conclusions: For situations where impressions of multiple implants are to be made, splinting impression copings with acrylic resin demonstrate superior results than the non-splinted technique and splinting with light-curing composite. Keywords: Implant impression, multiple implants, impression accuracy, impression-coping splinting. (Accepted for publication 6 October 2011.) INTRODUCTION The passive fit of an implant-retained prosthesis is an important factor in rehabilitation success. Any misfit between the prosthetic components and the implants may cause mechanical problems such as screw bending, loosening or fracture 1 3 or biological problems such as breakdown of the osseointegration between the implant and the surrounding bone. 4 6 Accurate impressions representing the precise positions of the implants in the oral cavity are important to successful passive fitting. 7,8 It is more critical to record and transfer the threedimensional position of the implants than it is to reproduce fine surface details. 7 Two basic impression techniques are commonly used for transferring implant positions from the intraoral cavity to a working cast: the direct (open tray) and the indirect (closed tray) technique. In the direct technique, the transfer copings remain in the impression and must be unscrewed before the impression is removed from the mouth. In the indirect technique, the transfer copings are retained on the implants after removal of the impression and must be repositioned in the proper imprints. 9 Many in vitro investigations have examined whether the accuracy of the direct technique could be improved by splinting the transfer copings. Different materials have been tested to splint the copings, such as dual-cure acrylic resin, 10 autopolymerizing acrylic resin, 10,12 and prefabricated acrylic resin bars. 13 In some studies, more accurate results were obtained when employing autopolymerizing acrylic resin instead of dual-polymerizing acrylic resin. 10 On the other hand, Assunção et al. reported no significant difference between casts obtained using acrylic resin-splinted or composite resin-splinted impression copings. 14 The results of studies on this topic have been inconsistent. Based on this data, this in vitro study aimed to evaluate the effect of splinting on implant impression accuracy when making impressions of edentulous arches containing multiple implants. 184 ª 2012 Australian Dental Association

Implant impression accuracy MATERIALS AND METHODS Master model and custom tray fabrication protocol Based on a patient case, a reference model of an edentulous maxilla was produced in transparent

A cast analogous to the reference model was produced in Type IV dental stone (Moldano Heraus Kulzer GmbH, Germany) for moulding custom trays.

2 Implant impression accuracy MATERIALS AND METHODS Master model and custom tray fabrication protocol Based on a patient case, a reference model of an edentulous maxilla was produced in transparent acrylic resin (Palapresss; Heraus Kulzer GmbH, Germany), including six Straumann Tissue Level implants (Institut Straumann AG, Basel, Switzerland) in a spread-out configuration (Fig. 1). A cast analogous to the reference model was produced in Type IV dental stone (Moldano Heraus Kulzer GmbH, Germany) for moulding custom trays. The 25 customized impression trays were fabricated using autopolymerizing acrylic resin (Meliodent, Bayer Dental, Germany) with a 3 mm space for the impression material. The trays were perforated to allow access to the transfer coping screws. Vertical stops were incorporated in all trays on both posterior sides to prevent over-seating of the impression trays. The trays were fabricated two days before impression. Impression procedures The trays were divided into five groups containing five casts each (Fig. 2): Experimental Group 1 (EG1): Screw-on synocta impression copings. Fig. 1 Transparent acrylic resin master cast. Experimental Group 2 (EG2): Screw-on synocta impression copings splinted with acrylic resin bar (non-sectioned acrylic bar). Experimental Group 3 (EG3): Screw-on synocta impression copings splinted with two separate acrylic resin bars (sectioned acrylic bars). Experimental Group 4 (EG4): Screw-on synocta impression copings splinted with light-curing composite resin bar (non-sectioned composite bar). Experimental Group 5 (EG5): Screw-on synocta impression copings splinted with two light-curing composite bars (sectioned composite bars). The acrylic resin splints were fabricated by injection of pattern resin (DuraLay, CG Lab Technologies Inc., Japan) into a drinking straw. 13 The bars were approximately 3 mm in diameter. After 24 hours, the bars were cut into appropriate lengths using diamond discs (Acurata Ò G+R Manhardt Dental e.k., Germany) and joined using the bread-brushing technique, thereby luting the ends of the bars to the impression copings. The impressions were made immediately after the material set. New resin bars were used for each impression. The same procedure was used for the fabrication of light-curing composite resin bars. A lightcuring high viscosity microhybrid composite (Ivoclar Vivadent Tetric Ceram System, Ivoclar Vivadent AG, Liechtenstein) was used to create the composite bars. Polyether impression material (medium body) (Impregum Penta Soft, 3M ESPE Dental, Medizin, Germany) was used for all impressions. Before the impressions were obtained, tray adhesive (3M ESPE, Seefeld, Germany) was applied evenly over the inner surface of each tray and extended 3 mm onto the outer surface. The adhesive was allowed to dry for 15 minutes. The impression material was syringed around the impression copings and at the same time placed in the custom trays. The elastomeric impression material specification (ADA ANSI) was used as an instructional guide. The model and loaded impression tray were placed in distilled water at 32 ± 2 C to simulate polymerization in the oral environment. 15 During the impression process, excess material was removed from the trays to expose the protruding sections of the impression posts. The impression material was allowed to set under a constant pressure of 2 kg exerted by EG-1 EG-2 EG-3 EG-4 EG-5 Fig. 2 Experimental groups used in the study. ª 2012 Australian Dental Association 185

3 DÖngül et al. Table 1. Technical characteristics of the ATOS SO High-End 3D Digitizer for Small Objects programme Technical data Measured points Measurement time 1 second Measurement area mm 2 Point spacing mm Camera pixels Sensor dimensions mm 2 a metal block. The impression was removed from the model three minutes later than the manufacturer s recommended setting time in order to compensate for the delay in polymerization while the assembly was at room temperature. The impression copings were unscrewed from the master model before the impression was removed. After removing the impressions from the model, implant analogues were screwed to the copings hand-tight. The impression analogue assemblies were poured 24 hours after the impression procedure using the same vacuum-mixed Type IV dental stone prepared according to the manufacturer s specifications (100 mg powder 30 ml water). The casts were allowed to set for one hour before being removed from the impressions. Measurements Deviations of the models were analysed in three dimensions (x, y, z) using the ATOS SO High-End 3D Digitizer for Small Objects programme (GOM Optical Measuring Techniques GOM mbh, Braunschweig, Germany) (Table 1). This programme is used in the manufacture of various medical devices and components, particularly complex small parts with high demands on accuracy and data quality. Distances between points of less than 0.02 lm can be measured. The models were placed on a rotating work table and scanned by a sensor probe. The probe was positioned near the models and two measuring cameras were mounted in front of the sensor head. The cameras, together with rotation of the table, scan the object from all sides and create an optimized triangulation for the smallest measuring areas. The resulting images were recorded after scanning. The images obtained were displayed on a computer monitor (Fig. 3). Each sample was compared with the original model. During this comparison, dimensional deviations were measured at predetermined points mesial, distal, vestibular and palatal to each implant, for a total of 24 points in each cast. Data analyses Statistical analyses were performed using the SPSS statistical programme package for Windows (SPSS, Chicago, USA). Descriptive and homogeneity tests were applied. Distortion values among the groups were analysed using one-way repeated measures ANOVA at a 0.05 level of significance. Tukey s post hoc test was performed to identify multiple comparisons. The results were considered significant at p values below RESULTS The accuracy of five different implant-level impression techniques for edentulous arches with multiple implants was compared. A total of 25 casts were divided into five groups containing five casts. The casts obtained using the direct impression technique exhibited small 1-1 1/1 [mm] _D d _V 5_D 6_P d _M d _P d _P 1_M d _P d _D d _V 2_D d _M 5_V d _D d _P d _D d _P d _M d _V _V d _M d _M d _V d Kullanid: ERVIN ADALI Sirket: CADEM A.S. Departman: KALITE KONTROL Bolge: BURSA Tarih: 04/08/2010 Proje: Parca: Parca.No: 1-1 Versiyon: V Sistem: ATOS 2 SO Cakis rma: Base Fit Fig. 3 Demonstration of measurements on casts. 186 ª 2012 Australian Dental Association

4 Implant impression accuracy Table 2. Amount of deviation obtained in each group Mean (lm) Std. Deviation (lm) 95% Confidence Interval for Mean Lower bound (lm) Upper bound (lm) EG EG EG EG EG deviations ( lm) from the master cast (Table 2). The highest accuracy was obtained in group EG2 (mean deviation: lm). The groups using acrylic bars (EG2 and EG3) displayed smaller deviations (12.70 lm and lm) from the master model than the light-curing composite resin groups (EG4 and EG5; lm and lm) and the non-splinted group (24.10 lm). The post hoc Tukey s test results indicated that the acrylic resin groups were statistically more accurate than the sectioned light-curing composite resin group (p = and p = 0.035) (Table 3). The splint design produced no significant difference in accuracy. DISCUSSION Maintenance of osseointegration is best achieved through passively fitting prostheses. 16,17 Accurate recording and transfer of implant location is a critical stage in fabricating a prosthesis with a passive fit. 8 It is more important to record the three-dimensional orientation of the implant as it is situated in the mouth than it is to record the surface in detail. 7,8 When an impression of multiple implants is necessary, the precision of the impression is even more critical. 18 An inaccurate impression may result in ill-fitting superstructures that may lead to mechanical and biological complications. 4,6,19 Although achieving a passive fit is practically impossible, 20 minimizing the inaccuracy should be the prosthodontist s goal. In a systematic review, Lee and et al. 21 investigated the accuracy of all published implant impression techniques and examined the clinical factors affecting impression accuracy. The authors concluded that there was no difference in the accuracy of pick-up and transfer techniques when there were three or fewer implants, but the pick-up technique produced superior results for multiple implants. 22 The present study investigated implant impression accuracy for multiple implants, and all impressions were made using the direct technique. Splinting impression copings were first introduced with the development of metal-acrylic resin implant fixed complete dentures for edentulous jaws. 23 Contradictory results were reported in the literature regarding the effect of splinting on implant impression accuracy, and many in vitro studies indicated that splinting is unnecessary. 17,24 Burawi et al. 24 compared the dimensional accuracy of a splinted impression technique to an unsplinted technique and reported that splinting resulted in a larger deviation from the master model, Table 3. Comparison of the groups Multiple comparisons Dependent variable: x (I) grp (J) grp Mean Difference (I ) J) Std. Error Sig. 95% Confidence Interval Lower bound Upper bound Tukey HSO ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ª 2012 Australian Dental Association 187

5 DÖngül et al. and that this was primarily associated with rotational discrepancies around the long axes of the implants. However, a number of authors presented splinting as the gold standard method to avoid impression coping movement and distortion of the impression and to ensure the accuracy of the master cast. 10,11 In agreement with the results of these previous investigations, a statistically significant difference between unsplinted and splinted groups was observed in this study. Groups in which splints were employed yielded better results than non-splinted ones. The mean deviation of the acrylic-resin splinted group was relatively small (12.7 lm) and comparable to the values reported by Wee 8 and Wenz 9 (11 23 lm). Acrylic resin is the most popular splinting material. Besides acrylic resin, impression plaster, 10 dual-cure acrylic resin, 10 orthodontic wire, prefabricated acrylic resin bars, 13 light-curing composite resin, 14 and carbon steel pins 25 have been used to splint the impression copings. In the present study, autopolymerizing acrylic resin and light curing composite resin were chosen as splinting materials. Autopolymerizing acrylic resin yielded better results, probably because of increased stiffness and greater stability. This advantage makes adaptation of this technique for clinical use more practical. Autopolymerizing acrylic resin is easier to use than composite resin as it does not require a dry environment or a specific light-curing device. 14 Autopolymerizing acrylic resin also has an economical advantage over light-curing composite resin. An ideal impression technique should provide excellent results while being easy to use, inexpensive and comfortable for the patient. 22 Autopolymerizing resin fulfils these requirements better than composite resin. In the present study, two different bar designs were used: sectioned bars which splinted the impression copings located on one side of the midline and nonsectioned bars running between the most distal impression copings on each side. Unexpectedly, the bar design did not affect the accuracy. The authors initially hypothesized that regardless of splint material, sectioned bars would provide better results because polymerization shrinkage is related to the volume of splinting material used, and the volume of the sectioned bars was smaller (EG4 and EG2). The authors hypothesized that there would be late distortion of the acrylic material but it would be nonsignificant, and the result of this study supported this. However, the results demonstrated that impression accuracy was affected only by the choice of splinting material. Polyether and polyvinyl siloxane are the materials of choice in implant impressions. Polyether produces high accuracy and reduces chair-time. 9 Although the use of a more elastic impression material is reported to be advantageous in evaluating the effect of splinting impression copings on implant impression accuracy, 26 polyether impression material was selected for the present study. An impression material must fulfil two requirements in direct implant impression techniques: it should be rigid enough to hold the impression copings and prevent accidental displacement, and it should produce minimal positional distortion between abutment replicas. 8 The authors concluded that polyether minimized the accidental displacement of impression copings when the abutment analogues were tightened. 8 CONCLUSIONS Within the limitations of this in vitro study, the following conclusions can be drawn: (1) even with standardized conditions, it was impossible to reproduce the exact position of implants in a cast model; (2) the most accurate casts were obtained in the splinted acrylic resin group (EG2); and (3) the sectioned bars (EG3 and EG5) demonstrated more deviation from the master model than the non-sectioned bars (EG2 and EG4). The clinical implication is that for situations where impressions of multiple implants in edentulous arches must be made and the pick-up implant impression technique is used, splinting impression copings with acrylic resin provide better results than either nonsplinted techniques or splinting using a light-curing composite. ACKNOWLEDGEMENTS The authors thank Institut Straumann AG, Switzerland and Batı Dental (local distributor of Institut Straumann in Turkey) for supplying the implant components, and 3M ESPE for providing impression materials for this research. This work was supported partly by the Research Fund of Istanbul University, Project number REFERENCES 1. Zarb GA, Schmidt A. The longitudinal clinical effectiveness of osseointegrated dental implants: the Toronto study. Part III. Problems and complications encountered. J Prosthet Dent 1990; 64: Sahin S, Cehreli MC. The significance of passive framework fit in implant prosthodontics: current status. Implant Dent 2001;10: Eckert SE, Meraw SJ, Cal E, Ow RK. Analysis of incidence and associated factors with fractured implants: a retrospective study. Int J Oral Maxillofac Implants 2000;15: Adell R, Lekholm U, Rockler B, Brånemark PI. A 15-year study of osseointegrated implants in the treatment of edentulous jaw. Int J Oral Surg 1981;10: Branemark PI. Osseointegration and its experimental background. J Prosthet Dent 1983;50: ª 2012 Australian Dental Association

6 Implant impression accuracy 6. Skalak R. Biomechanical considerations in osseointegrated prostheses. J Prosthet Dent 1983;49: Wee AG, Aquilino SA, Schneider RL. Strategies to achieve fit in implant prosthodontics: a review of the literature. Int J Prosthodont 1999;12: Wee AG. Comparison of impression materials for direct multiimplant impressions. J Prosthet Dent 2000;83: 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: 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: Cabral LM, Guedes CG. Comparative analysis of 4 impression techniques for implants. Implant Dent 2007;16: Vigolo P, Majzoub Z, Cordioli G. Evaluation of the accuracy of three techniques used for multiple implant abutment impressions. J Prosthet Dent 2003;89: Dumbrigue HB, Gurun DC, Javid NS. Prefabricated acrylic resin bars for splinting implant transfer copings. J Prosthet Dent 2000;84: Assunção WG, Tabata LF, Cardoso A, Rocha EP, Gomes EA. _ Prosthetic transfer impression accuracy evaluation for osseointegrated implants. Implant Dent 2008;17: American National Standards Institute American Dental Association. Specification No. 19 for Non-aqueous Elastomeric Dental Impressions. J Am Dent Assoc 1997;94: Addendum 1982;1105: Lundqvist S, Carlsson GE. Maxillary fixed prostheses on osseointegrated dental implants. J Prosthet Dent 1983;50: Spector MR, Donovan TE, Nicholls JI. An evaluation of impression techniques for osseointegrated implants. J Prosthet Dent 1990;63: Chee W, Jivraj S. Impression techniques for implant dentistry. Br Dent J 2006;201: Rangert B, Jemt T, Journeus L. Forces and moments on Brånemark implants. Int J Oral Maxillofac Implants 1989;4: Kan JY, Rungcharassaeng K, Bohsali K, Goodacre CJ, Lang BR. Clinical methods for evaluating implant framework fit. J Prosthet Dent 1999;81: Lee H, So JS, Hochstedler JL, Ercoli C. The accuracy of implant impressions: a systematic review. J Prosthet Dent 2008;100: Phillips KM, Nicholls JI, Ma T, Rubenstein J. Accuracy of three implant impression techniques: a three-dimensional analysis. Int J Oral Maxillofac Implants 1994;9: Brånemark P-I, Zarb GA, Albrektsson T. Tissue-integrated prostheses. Chicago: Quintessence, 1985: Burawi G, Houston F, Byrne D, Claffey N. A comparison of the dimensional accuracy of the splinted and unsplinted impression techniques for the Bone-Lock implant system. J Prosthet Dent 1997;77: Naconecy MM, Teixeira ER, Shinkai RS, Frasca LC, Cervieri A. Evaluation of the accuracy of 3 transfer techniques for implantsupported prostheses with multiple abutments. Int J Oral Maxillofac Implants 2004;149: Choi JH, Lim YJ, Yim SH, Kim CW. Evaluation of the accuracy of implant-level impression techniques for internal-connection implant prostheses in parallel and divergent models. Int J Oral Maxillofac Implants 2007;22: Address for correspondence: Dr Değer Öngül Department of Prosthodontics Faculty of Dentistry Istanbul University _Istanbul Üniversitesi Diş Hekimliği Fakültesi Protetik Diş Tedavisi AD Capa Istanbul Turkey degerkongul@yahoo.com ª 2012 Australian Dental Association 189

Effect of impression coping and implant angulation on the accuracy of implant impressions: an in vitro study

ORIGINAL ARTICLE DOI:10.4047/jap.2010.2.4.128 Effect of impression coping and implant angulation on the accuracy of implant impressions: an in vitro study Si-Hoon Jo, DDS, Kyoung-Il Kim, DDS, Jae-Min Seo,