Accuracy and Precision of Digital Impression with Reverse Scan Body Prototypes and All-on-4 Protocol: An In Vitro Research

Background/Objectives: Digital workflows for implant-supported full-arch restorations remain challenging. This study evaluated the accuracy and precision of digital impressions using reverse scan body (RSB) prototypes and intraoral scanners (IOSs) for rehabilitating fully edentulous patients following the All-on-4 protocol. Secondary objectives included comparing accuracy between expert clinicians and beginners, as well as desktop scanners and various RSB designs. Methods: An in vitro study was conducted using a fully edentulous mandible model with four Osstem TSIII implants. A final-year dental student and an expert clinician captured digital impressions using IOSs and desktop scanners. Four groups were analyzed: (A) original scan bodies with the IOS, (B) short RSBs with the IOS, (C) RSBs with desktop scanners (short sandblasted, long sandblasted, long coated), and (D) a control group using original scan bodies with a desktop scanner. Root mean square (RMS) values measured dimensional differences, with statistical analysis performed using the Wilcoxon signed-rank test and one-way ANOVA (α = 0.05). Results: A total of 42 scans were analyzed. No significant difference was found between expert and student for original scan bodies using the IOS (p = 0.220), while RSB prototypes showed significant differences (p = 0.008). No significant accuracy differences were noted between original scan bodies and RSBs with the IOS, but IOSs outperformed desktop scanners. Among RSBs scanned with desktop scanners, no significant differences were observed between designs. Conclusions: RSB prototypes are a viable alternative to original scan bodies for fully digital workflows in All-on-4 rehabilitations, with IOSs offering superior accuracy. However, proper training is crucial for optimizing RSB accuracy. Variations in height and coating did not impact overall accuracy.