Accuracy of implant impression techniques: 2D and 3D analysis

Purpose: To analyze in vitro the accuracy of different implants impression techniques with multifunctional guides simulating rehabilitation based on the all-on-4 scheme. Methods:  Six impression techniques were evaluated: palate coverage multifunctional guide / metal and acrylic resin splint transfers (PM); palate coverage multifunctional guide / acrylic resin splinted transfers (PR); palate coverage multifunctional guide / without splint transfers (PC); open palate multifunctional guide / metal and acrylic resin splint transfers (OM); open palate multifunctional guide / metal and acrylic resin splint transfers (OR) and open palate multifunctional guide / without splint transfers (OC). All the impression were made with polyvinyl siloxane impression material. Two methods of evaluation were used: measurement of vertical misfits (cervical adaptation – 2D) with a passive metal structure fabricated on the master cast (MM) and 3D evaluation of the overlap of digital images obtained by contact scanning. After verification of distribution and homoscedasticity data, Kruskal-Wallis test with Dunn post hoc (α=0.05) were used to verify the influence of the independent variables. Results: For the evaluation of vertical misfit (2D), statistical differences were found only for the OM group (203.04 µm) when compared to the PR group (151.61 µm) and to the MM group (142.78 µm). In the 3D evaluation, no difference was found between the groups when the three axis (x, y and z) were analyzed together. However, when separating the analysis by axis, difference was found between PM (214 µm) and OC (355 µm) for the X axis. For the Y axis, the PR (188 µm) was significant difference than the OM (588 µm). Conclusions: The group OM produced less vertical accurate (2D) casts than the groups PR and MM. In 3D evaluation, there was no differences when all axes were compared together, only separately, being PM more accurate than OC, and PR more accurate than OM, on the X and Y axes, respectively.