THE EFFECT OF THE TRANSFER ACCURACY OF DIFFERENT IMPRESSION COPINGS ON THE PASSIVE FIT OF CAD/CAM MILLED IMPLANT-SUPPORTED MANDIBULAR COBALT-CHROMIUM FRAMEWORK (IN-VITRO STUDY)

Introduction: Impression registration is a crucial procedure for accurate transfer of 3D implant position to the cast to obtain passive fit of the final restoration. Different impression techniques have been investigated to evaluate the efficiency of each technique regarding different implant angulations. Aim of The Study: To compare the efficiency of the open-tray and the clips impression copings for straight implants as well as different implant angulations. Materials and Methods: An epoxy model was used for placement of five implants (three implants of 0° angulation, one implant of 15° angulation, and another implant of 25° angulation). The specimens were grouped according to the impression technique used, using open-tray impression copings and clips impression copings, respectively. Stone casts were poured from both groups. The accuracy of the resultant implant position was evaluated through the passive fit of the CAD/CAM milled implant-supported framework constructed on the reference model, using Sheffield test. The passivity was assessed by measuring micro-gaps using optical microscope. Results: The study has shown that there was a significant difference between the two techniques only at implant #45 of 25° angulation, when screwing either the angled side (p =0.005) or the straight side (p < 0.001), while there was no statistically significant difference at implant #43 of 15° angulation and straight implants(#35, #33, middle implant), when screwing either sides (p> 0.005). Conclusion: Clips impression copings could be reliable to be used as an implant-level impression coping in different implant angulations to obtain a framework of acceptable passivity.