Trueness of Digital Versus Conventional Impressions in Mandibulectomy Models: An In Vitro Study

Background/Objectives: This in vitro study investigated the trueness of digital impressions (DIs) obtained using an intraoral scanner (IOS) compared to conventional impressions (CIs) on resin model replicas of mandibulectomy defects. Methods: Mandibulectomy resin models from 20 patients were used, including 10 partially edentulous (PE) and 10 completely edentulous (CE) patients. All models were scanned using an industrial scanner to obtain reference datasets. For CIs, silicone impressions were made in custom trays, poured into stone models, and subsequently scanned with the industrial scanner to create the test groups (n = 10 each): CI-PE and CI-CE. For the DI, an IOS (True Definition; TD) was used to directly scan the 20 models, yielding the groups DI-PE and DI-CE (n = 10 each). All test scans were superimposed on their corresponding reference scans, and trueness was assessed by calculating the mean absolute deviations (µm). Statistical analysis was performed to compare trueness across groups. Results: The mean deviations (µm) in CI-PE, CI-CE, DI-PE, and DI-CE were 26.49 ± 6.39, 23.10 ± 8.94, 76.64 ± 31.75, and 80.93 ± 33.21, respectively. Impression technique significantly affected the trueness results, with DIs showing higher overall deviations (78.78 ± 31.69 µm) than the CIs (25.24 ± 7.67 µm). No significant difference in trueness was found between partially and completely edentulous models. Conclusions: Digital impressions of mandibulectomy models made with a TD scanner had significantly lower trueness than CIs. However, the observed deviations remained within clinically acceptable limits (around 300 µm in 99.5% of the model scans), demonstrating the feasibility of TD for scanning mandibulectomy models.