Conventional Versus Digital Impressions for "All-on-Four" Restorations

Purpose: This study aimed to evaluate the most accurate impression technique for "All on Four" restoration, comparing conventional (CIG) and digital impressions (DIG). Materials and Methods: Patients randomly selected for this study were required to be edentulous in at least one arch, presenting with severe posterior mandibular or maxillary atrophy. All patients underwent full-arch immediate-load rehabilitations, which were fixed to a total of four implants (two axial and two tilted). Following implant placement, patients were stratified into two groups. Conventional pick-up was carried out in the control group, and digital impressions were performed in the test group. Following prosthetic rehabilitation, patients underwent intraoral digital radiographs to check for the presence of voids at the bar-implant connection and to evaluate accuracy. Three-, 6-, and 12-month follow-up examinations were performed. Results: A total of 25 patients received immediately loaded "All-on-Four" prostheses (17 maxillary, 13 mandibular) supported by four implants (total 120 implants), of which five received both maxillary and mandibular prosthetic rehabilitation (three patients in CIG, two patients in DIG). No implant dropouts occurred, showing a survival rate of 100%. The digital impression procedure required significantly less time than the conventional procedure (P < .001). Conclusion: Results demonstrate that it is possible to develop computer-aided design/computer-assisted manufacturing (CAD/CAM) cobalt-chromium full-arch rehabilitations with satisfactory accuracy using digital impression techniques.