Effect of scanner-specific CAD/CAM workflows and manufacturing pathways on the internal gap of crown frameworks

Accurate internal fit is important for the clinical performance of Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) crown frameworks. Accordingly, the present in vitro study aimed to evaluate the influence of scanner-specific CAD/CAM workflows and framework material/manufacturing pathways on the measured internal gap values of crown frameworks fabricated with a standardized digitally assigned cement space. A prepared maxillary central incisor on a phantom model was scanned using an intraoral scanner and an extraoral scanner. Crown frameworks were designed with a standardized cement space of 50 μm using the respective software. Zirconia frameworks were fabricated by milling, whereas cobalt–chromium frameworks were produced by direct metal laser sintering, generating four experimental groups ( n = 10). Internal gap values were measured in sagittal and frontal sections using the silicone replica technique and image-based analysis. Data were analyzed using the Shapiro–Wilk test and two-way ANOVA (α = 0.05). Scanner-specific workflow significantly affected internal gap values in both sagittal and frontal sections. In the sagittal section, zirconia frameworks showed lower internal gap values than Co–Cr frameworks; however, framework material/manufacturing pathway did not significantly affect frontal internal gap values. No significant scanner × framework material/manufacturing pathway interaction was observed in either sagittal or frontal sections. The highest sagittal internal gap was recorded for Co–Cr frameworks produced from extraoral scan data (103.23 ± 22.24 μm), whereas the lowest value was observed for zirconia frameworks produced from intraoral scan data (62.59 ± 20.12 μm). Overall, the measured internal gap values remained within commonly reported clinically acceptable ranges. Within the limitations of this in vitro study, scanner-specific CAD/CAM workflows and manufacturing pathways influenced the realization of the digitally assigned cement space as measured internal gap values. Therefore, the findings should be interpreted as workflow-dependent differences rather than direct evidence of scanner or material superiority.