Effect of axiopulpal line angle design and cement space settings on seating accuracy of CAD/CAM ceramic inlays: an in vitro study

Abstract

Objectives: This study investigated the effects of the axiopulpal line angle design and different cement space settings on the adaptation of indirect ceramic inlays. Methods: Standardized Class II cavities were prepared, scanned, and used to design ceramic inlays fabricated with a 5-axis milling unit. Based on the axiopulpal line angle design, the cavities were classified into sharp, rounded, and beveled groups. Each group was further subdivided (n = 10) according to cement space settings as 50, 100, and 50 & micro;m selectively increased to 100 & micro;m at the axiopulpal line angle (50/100 & micro;m). Milling accuracy, occlusal fit, and internal adaptation were examined using the triple-scan method. Statistical analyses were conducted using two-way analysis of variance with Tukey&apos;s post hoc test (alpha = 0.05). Results: In the sharp line angle group, the axiopulpal line angle region was under-milled, resulting in positive discrepancies. The 50 & micro;m cement space group demonstrated greater occlusal discrepancies regardless of the axiopulpal line angle design (p < 0.05). Even with increased cement space settings, the sharp line angle group exhibited statistically significant occlusal discrepancies. Nonsharp line angle groups demonstrated significantly smaller internal gaps and greater cement space uniformity when a cement space of 100 or 50/100 & micro;m was applied (p < 0.05). Conclusions: Nonsharp axiopulpal line angle designs improved milling accuracy and occlusal seating, resulting in smaller and more uniform internal gaps in the 100 and 50/100 & micro;m cement space setting. Clinical significance: Nonsharp axiopulpal line angle designs improve milling accuracy and seating in CAD/CAM ceramic inlays. When combined with a 100 & micro;m cement space or selectively increased cement space at the axiopulpal line angle area, thinner and more uniform cement gaps are achieved, which may improve clinical fit and long-term restoration stability.