An in vitro Study to Compare the Accuracy of Master Cast Fabricated by Three Different 10.5005/jp-journals-10012-1143 Transfer Techniques for Single Tooth CASE REPORT An in vitro Study to Compare the Accuracy of Master Cast Fabricated by Three Different Transfer Techniques for Single Tooth Implant Replacement using Open and Close Tray 1 Manesh Lahori, 2 Rahul Nagrath, 3 Yatharth Bhatia, 4 Anubhav Srivastav ABSTRACT Success in oral rehabilitation with dental implants can be attributed to precise surgical and prosthodontics techniques. The long-term success rate of osseointegrated implants has made implant supported prostheses the treatment option of choice for the treatment of missing teeth. With the predictable integration of implants, the emphasis is shifted toward precise prosthesis. An acceptable prostheses requires optimal accuracy in all steps of fabrication. Therefore, present study was undertaken to measure the accuracy between the resin model simulating the clinical situation of a maxillary posterior single-tooth implant and 12 groups of master casts fabricated by 3 different transfer impression techniques using polyvinylsiloxane (PVS) and polyether impression material with customized open and closed trays. Master casts fabricated for all the groups were analyzed with the help of profile projector to detect rotational position change of the hexagon on the implant replicas in the master casts in comparison to the resin model. The master cast using open tray technique with sandblasted coping using polyether material showed the minimum deviation and least rotational movement in the position of hexagon head of implant. Hence, the clinician should use sandblasted impression copings with polyether impression material to achieve a more accurate and precise orientation of the implant replicas on laboratory master casts for single-tooth implant restorations. How to cite this article: Lahori M, Nagrath R, Bhatia Y, Srivastav A. An in vitro Study to Compare the Accuracy of Master Cast Fabricated by Three Different Transfer Techniques for Single Tooth Implant Replacement using Open and Close Tray. Int J Oral Implantol Clin Res 2015;6(3):85-93. Source of support: Nil Conflict of interest: None INTRODUCTION Implant dentistry has become an important treatment modality to treat edentulism. The use of dental implants has greatly broadened the scope of restorative dentistry, 1 Principal and Head, 2,3 Reader, 4 Postgraduate Student 1-4 Department of Prosthodontics, KD Dental College and Hospital, Mathura, Uttar Pradesh, India Corresponding Author: Manesh Lahori, Principal and Head Department of Prosthodontics, KD Dental College and Hospital Mathura, Uttar Pradesh, India, e-mail: maneshlahori@gmail.com creating additional treatment options in treating simple to complex cases. 2 Success in oral rehabilitation with dental implants can be attributed to precise surgical and prosthodontics techniques. The long-term success rate of osseointegrated implants has made implant supported prostheses the treatment option of choice for the treatment of missing teeth. 1 An acceptable prostheses requires optimal accuracy in all steps of fabrication. To have a successful long-term result with implant prosthesis, a passive and precise fit of implant superstructure to an implant abutment is recommended. 1,2 The first step on which precision depends is accurately positioning the impression components and recording the implant position with the impression procedure. Different impression techniques can be used for single tooth implant prosthesis. The impression can be made either at the abutment level using a transfer coping or at an implant level using pick up coping. As Scott D. Ganz quoted proper impression techniques remains the foundation for proper prosthetic reconstruction. 3 The fabrication of accurate impressions and definitive casts is critical to achieve a passively fitting implant retained prosthesis. 4 Transfer of exact position and orientation of the implant to working casts is particularly important as any inaccuracy may result in improper fabrication of prosthesis leading to failure. 4 The purpose of this in vitro study was to evaluate the accuracy of single tooth implant impression techniques by evaluating the rotational changes of the implant hexagon in the laboratory master casts and comparing them to resin master model using three different transfer techniques with two different impression materials, using open and closed custom trays. This was done to obtain precise definitive cast for a single unit implant restoration. AIMS AND OBJECTIVES Aims To compare the accuracy of master cast fabricated by three different transfer techniques with open and close International Journal of Oral Implantology and Clinical Research, September-December 2015;6(3):85-93 85
Manesh Lahori et al tray using polyvinylsiloxane and polyether impression material. Objectives To obtain accurate master cast for single tooth implant restoration. To compare the accuracy of master casts obtained using three different impression copings for single tooth implant replacement. To compare the accuracy of open and close tray technique for single tooth implant replacement. To compare the accuracy of polyether and polyvinylsiloxane (PVS) impression materials for single-tooth implant replacement. MATERIALS AND METHODS An acrylic resin dentulous model of maxillary arch with missing right first molar was fabricated for the study. An external connection 5.0 10.5 mm implant was placed in the acrylic resin model in the right first molar edentulous region with the help of a thermoplastic stent. The second molar distal to the implant and the second premolar mesial to the implant were cut in a buccopalatal direction using a carborundum disk that was mounted on laboratory straight handpiece. The depth of sectioning was made constant with the help of surveyor. Surveying platform is fixed after achieving the desirable tilt. At the desirable height, i.e., at 4 mm depth, survey lines were marked on both the teeth. The teeth mentioned were sectioned so as to get two reference planes for the measurement of the angles between one of the side of the implant hexagon serving as the first plane and the sectioned tooth serving as the second plane. Thus two angles, one formed by the molar plane and the distopalatal side of the implant hexagon [mesial inclined angle (MIA)] and the other formed from the premolar plane and the mesiopalatal side of the implant hexagon [posterior inclined angle (PIA)], were obtained (Fig. 1). Fabrication of Custom Trays A total of 3 mm thick wax spacer was adapted to the resin master model from the right second molar to the left second molar for the purpose of making the custom tray. Three tissue stops were made on the right first premolar, left first premolar and left second molar teeth (Fig. 2). Polyvinylsiloxane impression was then made of the relieved master model and type III dental stone cast made. This stone cast was used to make custom impression trays using tray resin. A two-part mold of the master stone model along with the custom tray was fabricated with putty addition silicone impression material in a dental flask to make identical custom trays. This ensured that the internal dimensions of all the trays remained the same, thus making close fit, rigid custom trays. The impression trays had a window to allow access for the direct pick up coping (Fig. 3). Impression Making For Open Tray Technique The impression trays were coated with manufacturer recommended impression adhesive 5 minutes before each impression was made. Tray adhesive was applied evenly over the inner surface of each tray and extended approximately 3 mm onto the outer surface of the tray along the periphery. The adhesive was allowed to dry for 5 minutes before impression. The impression coping was secured on the implant using a torque wrench calibrated at 10 N-cm. Thirty PVS impressions and thirty polyether impressions were made according to the manufacturer s directions using one-step method of impression making. The medium body monophase, PVS impression material was loaded inside the impression tray and at the same time it was meticulously syringed around the impression coping to ensure complete coverage of the coping. The impression tray was lowered over the reference resin model until the tray was fully seated and maintained in Fig. 1: Reference resin model with angles MIA and PIA Fig. 2: Master model with spacer 86
An in vitro Study to Compare the Accuracy of Master Cast Fabricated by Three Different Transfer Techniques for Single Tooth Fig. 3: Two-part-mold of silicone impression material in a dental flask and custom tray over stone model A B C D Figs 4A to D: (A) Open tray impression with retained impression coping and implant analogue attached to coping; (B) Non modified square impression coping for open tray impression; (C) Modified Square impression coping for open tray impression; (D) Sandblasted Square impression coping for open tray impression position throughout the polymerization time. Impression material was allowed to set for 10 minutes from the start of mixing to compensate for the delayed polymerization time at room temperature. After the impression material had set, the coping screw was loosened and the tray removed with the transfer coping retained in them (Figs 4A to D). For Closed Tray Technique The impression trays were coated with manufacturer recommended impression adhesive 5 minutes before each impression was made. Tray adhesive was applied evenly over the inner surface of each tray and extended approximately 3 mm onto the outer surface of the tray International Journal of Oral Implantology and Clinical Research, September-December 2015;6(3):85-93 87
Manesh Lahori et al A B C D Figs 5A to D: (A) Closed tray impression with retained impression coping and implant analogue attached to coping; (B) Non modified tapered impression coping for closed tray impression; (C) Modified tapered impression coping for closed tray impression; (D) Sandblasted tapered impression coping for closed tray impression. directions using one-step method of impression making. The impression tray was lowered over the reference resin model until the tray was fully seated and maintained in position throughout the polymerization time. Impression material was allowed to set for 10 minutes from the start of mixing to compensate for the delayed polymerization time at room temperature. After the impression material had set, the tray was removed (Figs 5A to D). A total of 120 impressions were made which were divided into 12 groups with 10 impressions in each group (Table 1). Fabrication of the Master Cast Fig. 6: Master cast showing reference molar and premolar planes and angles formed by molar plane and distopalatal side of implant hexagon (MIA) and premolar plane and mesiopalatal side of implant hexagon (PIA) along the periphery. The adhesive was allowed to dry for 5 minutes before impression. The impression coping was secured on the implant using a torque wrench calibrated at 10 N-cm. Thirty PVS impressions and thirty polyether impressions were made according to the manufacturer s 88 Once the impressions were made, the implant replica (analog) was screwed on to the transfer coping retained within the impressions and then poured after 24 hours using type IV dental stone (Elite Rock, Zhermack). The casts were retrieved from the impressions after 2 hours. All casts were stored at room temperature for a minimum of 24 hours before measurements were made. All clinical and laboratory procedures were performed by the same operator.
An in vitro Study to Compare the Accuracy of Master Cast Fabricated by Three Different Transfer Techniques for Single Tooth Table 1: Twelve groups used in study Groups Material used Transfer coping Technique used 1 Polyvinylsiloxane medium body monophase Nonmodified square coping Open tray 2 Polyvinylsiloxane medium body monophase Square coping modified with tray adhesive Open tray 3 Polyvinylsiloxane medium body monophase Coping modified by sandblasting using aluminum Open tray oxide sand 4 Polyther medium body monophase Nonmodified square coping Open tray 5 Polyether medium body monophase Square coping modified with tray adhesive Open tray 6 Polyether medium body monophase Square coping modified by sandblasting using Open tray aluminum oxide sand 7 Polyvinylsiloxane medium body monophase Nonmodified ball top coping Closed tray 8 Polyvinylsiloxane medium body monophase Ball top coping modified by tray adhesive Closed tray 9 Polyvinylsiloxane medium body monophase Ball top coping modified by sand blasting using Closed tray aluminum oxide sand 10 Polyther medium body monophase Nonmodified ball top coping Closed tray 11 Polyther medium body monophase Ball top coping modified by tray adhesive Closed tray 12 Polyther medium body monophase Ball top coping modified by sandblasting using aluminum oxide sand Closed tray Profile Projector The profile projector is equipped with a screen with horizontal and vertical reference lines, and has a movable table that allows one to position the object being studied. A light source allows the projection of a magnified image of the object onto the screen in the form of a shadow so that the sharp edges of the projected silhouetted form become the reference points of measurements. All the measurements were measured by same operator to minimize source of error. The differences in degrees between the angles MIA and PIA measured on the reference resin model and the equivalent angles measured on the 120 master casts were analyzed statistically to determine which group produces more accurate impressions. Measurements All definitive casts were evaluated to check the rotational accuracy of implant replica heads using a profile projector. The two angles formed by the molar plane and the distopalatal side of the implant hexagon (MIA) and the premolar plane and the mesiopalatal side of the implant hexagon (PIA) in the resin model and the 120 master casts in groups 1 to 12 were measured using the Profile Projector (Fig. 6). RESULTS The molar plane angle (MIA) was found to be 24.9836º and the premolar plane angle (PIA) was 28.9017º in the resin master model. This was used as the reference to measure against master casts against which the angles formed in the respective groups were compared. ANOVA test revealed significant difference in the [deviation in mean of molar plane angle (DMIA)] and [deviation in mean of premolar plane angle (DPIA)] of twelve groups compared with standard measurement of resin master model. In this study p = 0.001 was considered as the level of significance. The deviation in mean reveals that the group 1 (nonmodified coping with closed technique using medium body PVS) have the maximum amount of variations while the group 10 (sand blasted coping with open technique using medium body polyether) showed the least variations in the molar and premolar plane angles (Table 2). ANOVA test revealed significant difference in the [deviation in mean of molar plane angle (DMIA)] and [deviation in mean of premolar plane angle (DPIA)] of twelve groups compared for three different impression transfer techniques. In this study p = 0.001 was considered as the level of significance. When nonmodified v/s sandblasted coping were compared it revealed a statistically significant difference but when modified v/s sandblasted technique were compared it revealed a unsignificant difference in the p value (Table 3). Student s unpaired t-test revealed significant difference in the [deviation in mean of molar plane angle (DMIA)] and [deviation in mean of premolar plane angle (DPIA)] of twelve group compared for open tray v/s closed tray technique. In this study p = 0.001 was considered as the level of significance. Mean value of DMIA and DPIA for open tray technique showed minimum deviations (Table 4). Student s unpaired t-test revealed significant difference in the [deviation in mean of molar plane angle (DMIA)] and [deviation in mean of premolar International Journal of Oral Implantology and Clinical Research, September-December 2015;6(3):85-93 89
Manesh Lahori et al Table 2: Deviation in MIA and PIA of all the groups with mean, standard deviation using one variable analysis Descriptives Groups n Mean Std. deviation F-value p-value DMIA 1 10 2.089 1.57405 2 10 1.716 0.96972 3 10 1.101 0.72158 4 10 1.004 0.42558 5 10 0.979 0.57964 6 10 0.608 0.31432 7 10 0.881 0.43905 3.951 <0.001 8 10 0.958 0.73124 9 10 0.818 0.36887 10 10 0.495 0.03951 11 10 0.971 0.5166 12 10 0.984 0.46455 Total 120 1.0503 0.79122 DPIA 1 10 3.167 2.28023 2 10 2.094 1.46669 3 10 1.364 0.94374 4 10 0.68 0.37381 5 10 0.904 0.59709 6 10 0.803 0.56902 7 10 1.149 0.80263 6.141 <0.001 8 10 0.966 0.65916 9 10 0.731 0.45261 10 10 0.509 0.13964 11 10 0.731 0.34391 12 10 1.068 0.72679 Total 120 1.1805 1.16346 Sum of squares df Mean square F Sig. DMIA Between groups 21.377 11 1.943 3.951 <0.001 Within groups 53.121 108 0.492 Total 74.498 119 DPIA Between groups 61.985 11 5.635 6.141 <0.001 Within groups 99.098 108 0.918 Total 161.082 119 plane angle (DPIA)] of twelve group compared for PVS v/s POLYETHER material. In this study p = 0.001 was considered as the level of significance. Mean values of DMIA and DPIA for polyether material showed minimum deviation (Table 5). DISCUSSION The objective of this in vitro study was to evaluate the accuracy of master cast by using three different transfer techniques. Significant difference in the mean premolar plane angle and mean molar plane angle of nonmodified group (Groups 1, 3, 5, 7) and modified groups (Groups 2, 4, 6, and 8)and sandblasted groups (9 12) when compared with standard measurement of resin master model. Least difference is found in respect to group 10. In this study p = 0.01 was considered as the level of significance (Graph 1). When comparing ranges, the maximum angular variation obtained for MIA in group 1 was 2º 17 minutes 30 seconds while in group 10 was 3 minutes 95 seconds. For PIA the maximum variation was 3º 9 minutes 71 seconds and for group 10 it was 36 minutes 60 seconds. This shows that the amount of rotational movement of implant components had considerably decreased from groups 1 to 11. Present study confirms the finding that the sandblasted impression copings results in more proper orientation of implant replicas and hence more 90
An in vitro Study to Compare the Accuracy of Master Cast Fabricated by Three Different Transfer Techniques for Single Tooth Table 3: Comparison of 3 impression transfer tecniques between nonmodified, modified and sandblasted coping. Intercomparison analysis done with help of ANOVA test n Mean Std. deviation F-value p-value Multiple comparisons DMIA Modified 40 1.0715 0.75568 Modified vs nonmodified Sanblasted 40 1.2625 1.0265 3.316 0.04 Modified vs nonmodified Total 120 1.0503 0.79122 DPIA Modified 40 1.1358 1.01397 Modified vs nonmodified DMIA DPIA Nonmodified 40 1.646 1.56666 6.375 0.002 Modified vs sanblasted Sanblasted 40 0.608 0.31432 Nonmodified vs sanblasted Total 120 1.1805 1.16346 Sum of df Mean square F Sig. squares Between 3.996 2 1.998 3.316 0.04 groups within groups 70.501 117 0.603 Total 74.498 119 Between 15.829 2 7.914 6.375 0.002 groups Within 145.253 117 1.241 groups Total 161.082 119 p-value 0.718 0.19 0.24 0.118 0.004 Table 4: Comparison of open tray and closed tray technique using t-test Group statistics Tray n Mean Std. deviation p-value DMIA Open 60 0.8597 0.51528 0.008 Closed 60 1.241 0.96084 DPIA Open 60 0.8318 0.59522 0.001 Closed 60 1.5292 1.45899 Tray DMIA DPIA Open 0.8597 0.8318 Closed 1.241 1.5292 Total 1.0503 1.1805 Molar plane angle (MIA) Premolar plane angle (PIA) Table 5: Comparison of polyether and PVS material using t-test Group statistics Materials n Mean Std. deviation p-value PVS 60 24.3335 1.48862 0.038 Polyether 60 24.8058 0.91356 PVS 60 28.1437 1.97892 0.004 Polyether 60 28.983 1.02944 accurate fabrication of master cast was achieved. This study suggests the use of abraded impression copings as this reduces the rotational movement of impression coping inside impression contributing to less prosthetic complications (Graph 2). Present study also compares deviation in two techniques (3, 4, 5, 6, 10, 11) open tray technique and (1, 2, 7, 8, 9, 12) closed tray. Deviation in mean premolar plane angle and deviation in mean premolar plane angle calculated for the groups used for open tray technique International Journal of Oral Implantology and Clinical Research, September-December 2015;6(3):85-93 91
Manesh Lahori et al A Graphs 1A and B: (A) Comparison of standard deviation of molar plane angle (MIA); and (B) premolar plane angle (PIA) between different study groups B Graph 2: Comparison of impression transfer techniques between nonmodified, modified and sandblasted coping. Intercomparison analysis done with help of ANOVA test showed less deviation than the closed tray technique groups. The use of Pick up impression technique is recommended, as it has a better axial orientation and it also minimizes the rotational movement of coping head. This will minimize the discrepancy during the fabrication of superstructure (Graph 3). To compare the accuracy of impreesion materials Groups (5 to 10) were fabricated using polyether showed less variations in comparison to groups (1, 2, 3, 4, 11, 12) fabricated using PVS. Polyether was found to have less deviation than PVS. In this study p = 0.001 was considered as the level of significance. In order to achieve a passive fit the amount of distortion in the impression phase must be minimized. Polyether impression material has a minimum distortion of all present impression materials, and this study confirms the same that the polyether is more accurate material in recording the spatial orientation of implant hexagon (Graph 4). Graph 3: Comparison of open tray and closed tray technique using t-test The limitations in the present study design were that the measured distortions did not completely evaluate the actual three-dimensional (3D) spatial distortion of the impressions. Only the discrepancies in axial rotations of the components were detected. Other dicrepancies which can occur in 3D space were not measured. Thus, such discrepancies may clinically result in a improper fit of the prosthesis. In future studies may be directed to evaluate the clinical importance of the 3D movements of impression copings inside the impression material. CONCLUSION Within the limitations of this study, the following conclusions were drawn: With respect to comparison of variability, based on standard deviation master casts obtained with the roughened impression copings showed a lower amount of rotational movement than the masters 92
An in vitro Study to Compare the Accuracy of Master Cast Fabricated by Three Different Transfer Techniques for Single Tooth position of the hexagon head of the implant than the casts obtained using closed tray technique. The master casts obtained using open tray technique with sandblasted coping using polyether material showed the minimum deviation and least rotational movement in the position of hexagon head of implant. Further clinical research will be necessary to confirm the results of the present in vitro study. REFERENCES Graph 4: Comparison of polyether and PVS material using t-test casts achieved with the nonmodified and modified impression. The master casts obtained from the polyether material showed less rotational movement than the casts obtained from PVS impression material. The master casts obtained by using open tray technique showed less rotational movement in the 1. Daoudi FM, Setchell JD, Searson JL. A laboratory investigation of the accuracy of two impression techniques for single tooth implants. Int J Prosthodont 2001;14(2):152-158. 2. Prithviraj DR, Pujari LM, Garg P, Shruthi DP. Accuracy of the implant impression obtained from different impression materials and techniques: review. J Clin Exp Dent 2011; 3(2):e106-111. 3. Ganz, SD. Obtaining impressions for the clinically successful implant-supported restoration. In Masters of Impressionism, Montage Media Corporation. August, 1997. 4. Vigolo P, Majzoub Z, Cordioli G. Evaluation of the accuracy of three techniques used for multiple implant abutment impressions. J Prosthet Dent 2003;89(2):186-192. International Journal of Oral Implantology and Clinical Research, September-December 2015;6(3):85-93 93