Comparative Evaluation of Impression Accuracy of Tilted and Straight Implants in All-on-Four Technique

PURPOSE: The aim of this in vitro study was to compare the accuracy of implant impressions in parallel and nonparallel implants of All-on-Four treatment plan. MATERIALS AND METHODS: A reference model containing 4 internal-connection implant analogs was fabricated according to All-on-Four treatment plan (2 anterior implants at 0 degree and 2 posterior implants at 30 degrees in relation to the perpendicular line). Twenty impressions of this model were made using open-tray impression technique. Impressions were poured with American Dental Association type 4 stone, and the positional accuracy of the implant replica heads in x-, y-, and z- axes was evaluated using a coordinate measuring machine. These measurements were compared with the obtained measurements from the reference model that served as control, and data were analyzed using independent test (α = 0.05). RESULTS: The results showed that the accuracy of the implant impressions did not show any significant difference between the tilted and straight implants except in y-coordinate (P = 0.012). CONCLUSION: Within the limitations of this study, the accuracy of the implant impressions did not differ for different implant angulations in All-on-Four treatment plan.