Comparison of impression techniques for a five-implant mandibular model.

Production of an accurate dental cast framework that meets the implant objective of passive fit demands an understanding of potential processing errors. Working casts fabricated from impressions using two different transfer copings, as provided by a leading implant manufacturer, were investigated for differences in accuracy. A five-implant mandibular model was used to produce seven casts by both the indirect and direct transfer coping techniques. Comparison was made by using a dental cast framework fitted to the master cast. Differences in distances measured between each group and the master cast were analyzed to establish differences between methods. For the model used, the direct technique produced more accurate working casts. A concern for potential impression distortion given the specific clinical situation underscores the method of choice.     

In vitro comparison of master cast accuracy for single-tooth implant replacement

STATEMENT OF PROBLEM: The inaccuracy in transferring the position of the hexagonal head of a single implant to the working cast can result in a final single tooth crown, which clinically may present occlusal and/or interproximal contacts that are different from those contacts on the master cast obtained by the technician. PURPOSE: This in vitro study evaluated the accuracy of the master casts obtained using square pick-up impression copings for single-tooth replacement. Copings used were (1) copings as sold by the manufacturer, and (2) copings modified by sandblasting and coating with impression adhesive their roughened surfaces before final impression procedures. MATERIAL AND METHODS: A polymeric resin model with a standard single implant was used to simulate a clinical situation. A group of 20 impressions were made using nonmodified impression copings; a second group of 20 impressions were fabricated with modified copings. Master casts fabricated for both groups were analyzed to detect rotational position change of the hexagon on the implant replicas in the master casts in reference to the resin model. RESULTS: The rotational position changes of the hexagon on implant replicas were significantly less variable in the master casts obtained with the modified impression copings than in the master casts achieved with the nonprepared copings. CONCLUSION: Improved precision of the impression was achieved when the adhesive-coated copings were used.     

Accuracy of 3 conceptually different die systems used for implant casts.

STATEMENT OF PROBLEM: Given that meticulous implant prosthodontic procedures are recommended to obtain the best possible intraoral fit, the die systems used for multi-implant casts warrant further investigation. PURPOSE. The purpose of this in vitro study was to compare the accuracy of implant casts fabricated from 3 conceptually different die systems at the solid, sectioned, and repeated stages. MATERIAL AND METHODS: Thirty direct transfer implant impressions were made of the master cast with a polyether impression material. Ten experimental implant casts were fabricated for each of the 3 different die systems tested: double-pour (Pindex), plastic base (DVA), and die tray (KO Tray). The solid experimental casts were sectioned and then removed from the die system 30 times. Linear distances between steel balls placed on each abutment replica were measured with a traveling microscope to determine the accuracy of the experimental casts at different stages. Data were analyzed with repeated-measures analysis of variance (alpha=.05) and the post hoc Ryan-Einot-Gabriel-Welsch multiple-range test (REGWQ). RESULTS: Repeated-measures analysis of variance revealed a significant interaction between the die systems and different stages (P=.0432). REGWQ showed the die tray system to be significantly more accurate at the solid than at the sectioned and repeated stages. The die tray system was significantly less accurate than the double-pour and plastic base systems at the sectioned stage. CONCLUSION: Within the limitations of this study, the use of a double-pour or plastic base die system is recommended when sectioned dies are needed for a multi-implant-retained prosthesis.     

Precision of Fit to Implants: A Comparison of Cresco™ and Procera® Implant Bridge Frameworks

Background: The Cresco? (Astra Tech AB, Mölndal, Sweden) method aims to reduce the inevitable distortions when cast metal frameworks for implant‐supported prostheses are fabricated. However, limited data are available for the precision of fit for this method. Purpose: To measure and compare the precision of fit of Cresco‐ and computer numeric controlled (CNC)‐milled metal frameworks for implant‐supported fixed complete prostheses. Materials and Methods: Two groups of frameworks were fabricated according to the Cresco method, either in titanium (Cresco‐Ti, n = 10) or in a cobalt‐chrome alloy (Cresco‐CoCr, n = 10). A third group comprised CNC‐milled titanium frameworks (Procera® Implant Bridge [PIB], Nobel Biocare AB, Göteborg, Sweden), made from individual model/pattern measurements (PIB, n = 5). Measurements of fit were performed by means of a coordinate measuring machine linked to a computer. The collected data on distortions were analyzed. Results: Overall, a maximal three‐dimensional range of center point distortion of 279 µm was observed for measured frameworks. The framework width (x‐axis) decreased for Cresco‐CoCr, but increased in Cresco‐Ti and PIB; Cresco‐CoCr compared to Cresco‐Ti (p = .0002) and Cresco‐CoCr compared to PIB (p < .0001). In vertical dimension (z‐axis), less distortions were present in PIB compared to Cresco‐CoCr (p = .0007) and in PIB compared to Cresco‐Ti (p < .0001). Conclusions: None of the frameworks presented a perfect, completely “passive fit” to the master. Although the direction of distortions varied, the horizontal distortions were of similar magnitudes. However, the PIB frameworks had statistical significant less vertical distortions as compared to the Cresco groups.     

Evaluation of Accuracy of Direct Transfer Snapon Impression Coping Closed Tray Impression Technique and Direct Transfer Open Tray Impression Technique: An In Vitro Study

Accuracy of the implant impression technique is one of the key factor determining the strain free fit of the prosthesis fabricated which influences the treatment success. Two implant impression techniques namely the closed tray technique with transfer coping and open tray technique were evaluated for accuracy with stone casts obtained from them. Casts were evaluated using a custom constructed bar on strain gage (SYSCOM) and abutment coordinates using Coordinate Measuring Machine (TESA micro-HITE). The statistical analysis with one way ANOVA and Mann–Whitney tests show that the casts obtained with open tray technique were accurate than the casts of closed tray technique (significance P < 0.001). Direct transfer impression technique with less number of components ensures the high accuracy of transfer of implant positions from master cast to the laboratory cast compared to the indirect transfer impression technique.     

Comparison of impression materials for direct multi-implant impressions

STATEMENT OF PROBLEM: Given that meticulous implant prosthodontic procedures are recommended to obtain the best possible intraoral fit, impression materials that are suitable for use with a direct impression technique warrant further investigation. PURPOSE: This in vitro study compared the amount of torque required to rotate a square impression coping in an impression and evaluated the accuracy of solid implant casts fabricated from different impression materials. MATERIAL AND METHODS: Two direct transfer implant impressions were made using 8 impression materials; the torque required to rotate an impression coping in the impressions was calculated. Ten direct transfer implant impressions were made from the master model and poured in a die stone (Resin Rock) for 3 of the 8 initial impression material groups. Linear distances between steel balls placed on each abutment replica were measured with a traveling microscope to determine distortion in the impression procedure for each group. Data were analyzed (P =.05) with ANOVA and Ryan-Einot-Gabriel-Welsch multiple range test for post hoc. RESULTS: With a 1-way ANOVA, average torque values among the material groups differed significantly (P =.001). Polyether (medium consistency) was found to produce the highest overall torque values, followed by addition silicone (high consistency), and then polysulfide (medium consistency). Statistically significant difference was also found among the 3 material groups' mean absolute cast error using a 1-way ANOVA (P =.0086). Implant casts made from polyether (medium) or addition silicone (high) impressions were significantly more accurate than casts made from polysulfide medium impressions. CONCLUSION: On the basis of the results of this study, the use of either polyether (medium) or addition silicone (high) impression is recommended for direct implant impressions.     

Effect of vertical misfit on strain within screw-retained implant titanium and zirconia frameworks

PurposeTo assess the implication of vertical misfit on strain within implant frameworks manufactured in titanium or zirconia.MethodsA master model was fabricated by inserting a Brånemark implant in left side of a mandibular model in the area of the first premolar and the first molar. This model was used to fabricate identical frameworks, five in titanium and five in zirconia. A single strain gauge was mounted on the occlusal surface of each framework to assess strain development as a result of framework fitting. In addition, the peak-to-peak strain amplitude was measured for each framework to determine the strain pattern fluctuation. The vertical gap of the framework–implant interface was measured using a measuring microscope, when only one screw was tightened (1-screw test) and when both screws were tightened (2-screw test). The vertical fit of the frameworks was altered by adding one to three layers of 30 μm steel shims on one of the implants.ResultsFor all fitting conditions, measurable amount of strains were recorded, however, as the vertical misfit was introduced, linear increase in framework strain was detected. The titanium and zirconia frameworks exhibited similar strain activities. A direct relationship was observed between the framework strain and vertical gap.ConclusionsFramework misfit clearly influenced the framework strain magnitude and pattern. The framework material did not affect the framework strain for a similar level of misfit.     

Volumetric Misfit in CAD/CAM and Cast Implant Frameworks: A University Laboratory Study

Purpose: To compare the volumetric misfit between implant restorative platforms of implants and implant frameworks manufactured with two different technologies. One set of implant frameworks was made with a CAD/CAM protocol and a tactile probe; the second protocol consisted of frameworks made with the lost‐wax technique and conventional casting technology. Materials and Methods: In this laboratory study, an acrylic resin model with five “inter‐foraminal” implants was used as the “patient” model. Implant level impressions were made, and 10 definitive master casts were fabricated. The casts were verified using an index made on the patient model. Five cast high palladium noble alloy and five CAD/CAM titanium alloy frameworks were fabricated. The patient's implants and the frameworks’ implant restorative platforms were scanned with a tactile probe, and the data were digitized. The digitized implant restorative platforms of the frameworks were fit onto the patient's digitized implants via a software program, in a process called “lofting.” This computerized procedure simulated a 1‐screw test; the process was performed on both sides. The volumetric misfit between the implant restorative platforms of the frameworks and the patient's implants were measured. A Welch's t‐test was used to determine significant differences (p < 0.05) between the misfit of the two technologies. Wilcoxon Signed‐Rank tests were used to evaluate differences between the right and left sides. Results: On average, the volumetric misfit of the CAD/CAM frameworks was 1.8 mm³ less than the volumetric misfit of the cast alloy frameworks (p < 0.05). The Wilcoxon Signed‐Rank tests showed no significant differences between the right and left sides within both systems (p > 0.05). Conclusions: The scanning technology and computer software program used in this study demonstrated that the CAD/CAM implant frameworks had statistically significantly less volumetric misfit when compared with the cast implant frameworks. There were no significant differences between the right and left 1‐screw tests within the same type of frameworks.     

An In Vitro Study to Compare the Accuracy of the Master Cast Fabricated by Four Different Transfer Impression Techniques for Single-Tooth Implant Replacement

Single tooth implant retained crowns have become a recognized technique for the replacement of the missing teeth. With the predictable integration of implants, the emphasis is shifted towards precise prosthesis. Minor movement of the impression coping retained inside the impression material can occur during all the procedures, leading to the three-dimensional spatial inaccuracies in the master casts. Therefore, the present study was undertaken with the purpose to evaluate the accuracy of single-tooth implant impression techniques using four different impression copings, so as to obtain a precise definitive cast for a single-unit implant restoration. A maxillary acrylic resin model with a standard single implant in the first molar region was used to simulate a clinical situation. A total of 60 impressions were made with polyvinylsiloxane impression material, which were divided into four groups of 15 impressions each. Group I used non-modified square impression coping, while in group II, III and IV square impression coping were modified differently. Master casts fabricated for all the groups were analyzed to detect rotational position change of the hexagon on the implant replicas in the master casts in reference to the resin model. The master casts obtained with the roughened and adhesive-coated impression copings showed a lower amount of rotational movement than the masters casts achieved with the non-modified impression copings. Hence, the clinician should use sandblasted and adhesive coated impression copings to achieve a more accurate and precise orientation of the implant replicas in the laboratory master casts in single-tooth implant restorations.     

Master cast accuracy in single-tooth implant replacement cases: an in vitro comparison. A technical note

PURPOSE: This in vitro study evaluated the accuracy of master casts obtained by using (1) copings modified by sandblasting and coating their roughened surfaces with impression adhesive before final impression procedures and (2) gold machined UCLA abutments as impression copings in final impression procedures for single-tooth implant replacement cases. MATERIALS AND METHODS: A polymeric resin model with a standard single implant was used to simulate a clinical situation. A group of 20 impressions were made using square impression copings sandblasted to roughen their external surfaces at a supragingival level and then coated with Impregum polyether adhesive; a second group of 20 impressions were made using gold machined UCLA abutments as impression copings. The castable part of the UCLA abutments was secured with resin to the gold machined section of the UCLA abutment to prevent movement of the castable part itself on the gold machined portion during the impression procedures; the castable portion of the UCLA was also coated with the Impregum polyether adhesive to improve the stability of the gold machined UCLA abutment inside the impression material. Master casts fabricated for both groups were analyzed to detect rotational position change of the hexagon on the implant replicas in the master casts with reference to the resin model. RESULTS: The rotational position changes of the hexagon on implant replicas were significantly less variable in the master casts obtained using gold machined UCLA abutments as impression copings than in the master casts achieved with the roughened square impression copings. DISCUSSION: Improved precision of the impression was achieved when the gold machined UCLA abutments were used as impression copings. CONCLUSION: This report suggests that using gold machined UCLA abutments as impression copings in the final impression procedures can enable the clinician to achieve a more accurate orientation of the implant replicas in the laboratory master casts for single-tooth implant replacement cases.     

The effect of internal versus external abutment connection modes on crestal bone changes around dental implants: a radiographic analysis

Background: To the best of our knowledge, the influence of external versus internal implant–abutment connections on crestal bone remodeling has not been reported. The aim of the present study is to investigate the influence of the abutment connection on peri‐implant crestal bone levels (CBLs) using radiographic recordings. Methods: Radiographic recordings from 40 single‐tooth implants (20 external and 20 internal octagonal connections; one implant/patient) in 40 patients (15 males and 25 females; mean age: 54.3 years) were selected for analyses. The radiographic evaluation included the following: 1) linear bone change (LBC); 2) dimensional change (DC); and 3) angle between the implant and adjacent bone (AIB). Differences in LBC, DC, and AIB between implant placement and 1 year after loading for each system were evaluated using a paired t test. Comparison of LBC, DC, and AIB between systems at 1 year after loading was done using analysis of covariance. The significance level was set at P ≤0.05. Results: Radiographic CBLs (LBCs) were reduced at 1 year after loading compared to those at implant placement to reach statistical significance for the external connection (P = 0.000) but not the internal connection (P = 0.939). CBL changes were significantly greater for the external compared to the internal connection (P = 0.000). Similarly, the DC for the external connection was significantly greater compared to that for the internal connection (P = 0.004). Conclusion: Within the limitations of this study, the implant–abutment connection technology appears to have a significant impact on peri‐implant CBLs, with the external connection paralleled by a significant reduction of CBLs.     

The Effects of Custom Tray Material on the Accuracy of Master Casts

Purpose The accuracy of master cast reproduction by a polyvinylsiloxane impression material using two visible-light-curing resin and an autopolymerizing polymethyl methacrylate resin custom tray materials was investigated. Materials and Methods Custom trays were fabricated from a master cast that had three index points marked on both the inner and outer vestibules. Impressions were made of the master cast using Extrude and then poured in Die Keen Green stone. The distances between the reproduced index points were measured to ±0.01 mm with a traveling microscope and the algebraic norms calculated for each tray material. Results No differences (p > .05) were found in the dimensions of the inner index points, while the separations of the outer index points indicated that there were differences in the accuracy of reproduction (p > .01) by the three tray materials. The index points reproduced on the casts, compared with the master cast, were closer together for the Triad Blue trays than for the TruTray and Ontray impression trays. Conclusions All three tray materials produced acceptable casts, but the greatest accuracy was achieved with TruTray, followed by Ontray. Triad Blue produced casts that were slightly smaller than the master. In practice, the small measured differences in cast dimensions may not have clinical significance.     

Accuracy of Impression Techniques for Implants. Part 1 – Influence of Transfer Copings Surface Abrasion

Purpose: This study evaluated the influence of surface abrasion of transfer copings to obtain a precise master cast for a partially edentulous restoration with different inclinations. Materials and Methods: Replicas (N = 30) of a metal matrix (control group) containing two implants at 90° and 65° in relation to the benchtop were obtained using a polyether impression material and three impression techniques: square impression copings splint with dental floss and autopolymerizing acrylic resin (TRS), square impression copings abraded with aluminum oxide (TA), and square impression copings abraded with aluminum oxide and adhesive‐coated (TAA). The replicas obtained in type V stone were digitalized, and the images were exported to AutoCAD software to perform the readings of possible degree alterations in implant inclinations. The results were submitted to analysis of variance (ANOVA) and Tukey test (α < 0.05). Results: Comparing the techniques with regard to the 90° implant inclination, no statistical difference was observed between the three techniques and the control group. Analyzing the three techniques with regard to the 65° implant inclination, no significant difference was seen between technique TA and the control group. Conclusions: Technique TA presented more accurate master casts than TRS and TAA techniques. The angulated implant (65°) tended to generate more imprecise master casts than implants perpendicular to the surface.     

Fabricating Low-Fusing Metal Casts for More Accurate Implant Prosthodontics

An important factor that affects the clinical success of dental implants is the way stresses are transferred to the bone via the implant framework and fixture. An ill-fitting implant framework will contribute to these stresses and may result in catastrophic failure of the prosthesis or one of the components and/or fixtures, in addition to possible alveolar bone loss. Many factors may contribute to the difficulty of achieving a passive fit on a complete-arch implant framework. A technique for producing an accurate master cast by using a low-fusing metal is described. The low-fusing metal is dimensionally more accurate than conventional gypsum products. The technique does not require a significant change from conventional chairside and laboratory procedures for complete-arch master cast impressions, and should result in a more passively fitting framework.     

Impression techniques and misfit-induced strains on implant-supported superstructures: an in vitro study

The purpose of this study was to compare misfit-induced strains on implant-supported superstructures fabricated by two impression techniques and two different elastomeric impression materials. A master cast hosting four Straumann implants was constructed. On this cast, a total of 21 implant-level impressions were made by the direct technique using a polyether impression material and synOcta screwed aluminum impression caps (PE-D), and by the indirect technique using polyether (PE-IN) or polyvinylsiloxane impression material (VPS-IN) with snap-on impression caps and synOcta plastic positioning cylinders. Two casts were randomly selected from each group of seven, and a total of four screw-retained superstructures, supported by either two or four implants (one of each type on both casts), were cast in a gold alloy for each group. Linear strain gauges were bonded on the superstructures, and misfit-induced strains were recorded during superstructure connection on each of the working casts and on the master cast using a data acquisition system and corresponding software at a sample rate of 10 kHz. Connection on the implants in the master cast increased strains considerably on most of the superstructures, in comparison with strain gradients measured when the superstructures were connected on the casts from which they were fabricated (P <.05). The differences in strain amplitude between connection on the cast from which the superstructure was fabricated and on the master cast were higher for superstructures fabricated by PE-D than for those fabricated by PE-IN and VPS-IN. The snap-on indirect impression technique for Straumann implants leads to acceptable superstructures, regardless of the impression material used.     

Accuracy of implant casts generated with splinted and non-splinted impression techniques for edentulous patients: an optical scanning study

Background: The accuracy of implant casts generated with various impression techniques was mainly investigated in vitro resulting in limited clinical data. Purpose: (1) To compare the three‐dimensional (3‐D) accuracy of splinted and non‐splinted impression techniques to the control casts (verification jigs) that had been used for actual patient treatment; and (2) to determine the maximum level of clinically undetectable misfit. The null hypothesis was that there would be no significant difference in the accuracy of casts generated with different impression techniques. Materials and methods: The implant casts used for the prosthetic rehabilitation of 12 edentulous jaws with CAD/CAM zirconia, implant‐fixed complete dental prosthesis (IFCDP) were included in this study. Intraoral acrylic jigs were used to fabricate index casts. Splinted and non‐splinted, open‐tray techniques were used to generate two casts. Optical scanning acquisition of the x‐coordinates, y‐coordinates and z‐coordinates of the implant positions for each individual cast was performed. The “best fit” algorithm was used with computer software to superimpose the scanning datasets. Group I (n=12) included casts from the splinted impression technique vs. acrylic jig casts, and group II (n=12) included casts from non‐splinted technique vs. jig casts. Results: The paired t‐test and Wilcoxon's signed ranks test were used to compare the 3‐D discrepancies within and between groups I (splinted vs. jig) and II (non‐splinted vs. jig), respectively. Significant difference was found at the x‐axis, y‐axis and 3‐D between groups I and II (P<0.05), but not in the vertical z‐axis (P>0.05). Within subject, global 3‐D discrepancies between groups I and II were significantly different (P<0.05), corroborated by in vivo observations of clinical fit. Implant position in the arch affected the 3‐D accuracy of casts for both anterior and posterior implants (P<0.05). Conclusion: The splinted technique generated more accurate master casts than the non‐splinted technique for one‐piece IFCDPs in edentulous jaws and the null hypothesis was rejected. These clinical implications demonstrate improved accuracy of splinted impression techniques compared with the non‐splinted technique. For the external connection, the implant system used in this study, a 3‐D misfit ranging from 59 to 72 μm, may be considered the maximum discrepancy resulting in an acceptable clinical fit with one‐piece IFCDPs.     

Evaluation of impression accuracy for osseointegrated implant supported superstructures

STATEMENT OF PROBLEM: An often-debated issue still exists concerning implant impression techniques, whether to splint impression copings. Different configurations are available for these copings for a variety of manufacturers' implant systems. PURPOSE: This study evaluated and compared 4 impression techniques in terms of their dimensional accuracy to reproduce implant positions on working casts. MATERIAL AND METHODS: A master model was designed to simulate a clinical situation. Impressions were made using 4 techniques: (1) tapered impression copings not splinted; (2) squared impression copings not splinted; (3) squared impression copings splinted with autopolymerizing acrylic resin; and (4) squared impression copings with a lateral extension on one side not splinted. Reference points machined onto the master model and onto special healing abutments were compared after abutments were transferred to casts using the 4 techniques. Measurements were made using a Reflex microscope, capable of recording in the x-, y-, and z-dimensions. RESULTS: The dimensional accuracy was high and, although statistically significant (P =.022; power > 80%), a maximum distortion difference of only 0.31% was registered. CONCLUSION: The dimensional accuracy of all the techniques was exceptional and the observed differences can be regarded as clinically negligible.     

Evaluation of the accuracy of implant-level impression techniques for internal-connection implant prostheses in parallel and divergent models

PURPOSE: This study evaluated the accuracy of 2 implant-level impression techniques (direct nonsplinted and splinted) for the fabrication of multi-unit internal-connection implant restorations in 2 simulated clinical settings (parallel and divergent) using a laboratory model. MATERIALS AND METHODS: A dental stone master model was fabricated with 2 pairs of implant replicas. One pair simulated a parallel clinical condition and the other an 8-degree-divergent condition. Ten stone casts were made from vinyl polysiloxane impressions of the master model for each impression technique. Half of the samples were created by a direct nonsplinted technique (square impression copings, custom tray), and the other half were made by a direct splinted technique (square impression copings splinted with autopolymerizing acrylic resin, custom tray). Four strain gauges were fixed on each metal framework to measure the degree of framework deformation for each stone cast in half-Wheatstone-bridge formations. Deformation readings were made twice in 4 directions (anterior, posterior, superior, and inferior). Deformation data were analyzed using repeated-measures analysis of variance at a .05 level of significance. RESULTS: No significant difference in deformation was found between the direct nonsplinted and splinted samples in either simulated clinical condition (P > .05). No significant difference in deformation was found between the techniques regardless of condition (P > .05). CONCLUSIONS: Within the limitations of this study, using a 2-implant model, the accuracy of implant-level impressions for internal-connection implant restorations was similar for the direct nonsplinted and splinted techniques in settings with divergence up to 8 degrees.     

Dimensional accuracy of an epoxy resin die material using two setting methods

STATEMENT OF PROBLEM: Resinous die materials have several important advantages including strength, abrasion resistance, and detail reproduction. Despite these advantages, the shrinkage of resinous die materials during polymerization has limited their widespread acceptance. PURPOSE: This study determined whether a retarded setting reaction could improve the accuracy of an epoxy resin die system, and compared the accuracy of this epoxy resin system with gypsum-based die materials. MATERIAL AND METHODS: Four groups were compared: an epoxy resin manipulated according to manufacturer's instructions (Ivoclar, Schaan, Liechtenstein); the same epoxy resin manipulated to undergo a retarded set; a high-strength high-expansion gypsum (Die Keen); and a resin-filled gypsum (Resin Rock). Ten dies were fabricated for each material from a master metal model using conventional prosthodontic laboratory techniques. The mean of 3 independent measurements recorded using a toolmaker's microscope and digital positioners was used to describe each die. RESULTS: One-way ANOVA revealed that significant differences existed among the materials (P <.0001). Tukey's multiple comparisons testing ranked the dies as follows, from largest to smallest: high-strength high-expansion gypsum, resin-filled gypsum, master metal model, retarded epoxy, and manufacturers epoxy (P <.05). CONCLUSION: Retarding the setting reaction of an epoxy resin die material improved its accuracy. Of the materials tested, retarded set epoxy dies had the least mean dimensional change from the metal master. Epoxy resin die materials had a net shrinkage, but the gypsum-based materials had a net expansion. The epoxy resin materials exhibited more variability than the gypsum-based materials.     

Three‐Dimensional Accuracy of Guided Implant Placement: Indirect Assessment of Clinical Outcomes

Purpose: Precise preoperative implant planning and its exact intraoperative transfer are crucial for successful implant‐supported rehabilitation of partially or completely edentulous patients. In the present pilot study, optical laser scanning was used to evaluate deviations between three‐dimensonal computer‐assisted planned and actual implant positions by indirect methods. Material and Methods: Five patients receiving a total of 15 implants were included in this study. The used planning software was SimPlant 12.0 (Materialise Dental, Leuven, Belgium) to visualize the implant positions, and with an appropriate guided surgery protocol (Navigator?, Biomet 3i, Palm Beach Gardens, FL, USA) implant positions were implemented via tooth‐supported stereolithografic surgical guides. All implants (Osseotite?, Biomet 3i) were inserted in a flapless approach and immediately provided with prefabricated temporary splinted restorations. Intraoral pickup impressions were taken postoperatively, and the implant positions of the master casts were compared with presurgical casts. Implant replica deviations were evaluated by three‐dimensional optical laser scanning providing distances and angulations between implant replicas. Results: Overall, the postsurgical implant replica positions were found to deviate from the positions in the preoperative cast by a mean of 0.46 ± 0.21 mm (range: 0.09–0.85 mm). Positional deviations were 0.27 ± 0.19 mm (range: 0.04–0.60 mm) along the x‐axis representing the buccal‐lingual directions, 0.15 ± 0.13 mm (range: 0.0–0.34 mm) along the y‐axis representing the ventrodorsal direction, and 0.28 ± 0.19 mm (range: 0.02–0.59 mm) along the z‐axis representing cranial and apical directions. Rotational deviations amounted to 14.04 ± 11.6° (range: 0.09–36.47°). Conclusions: The results of this pilot study demonstrate precise transfer of implant replica position by means of simulated guided implant insertion into a preoperative cast and a postoperative cast obtained from impressioning. Further studies are needed to identify appropriate evaluation techniques and mechanisms to increase the transfer precision of three‐dimensional planning and guiding systems.