Marginal and internal adaptation of monolithic computer-aided design and computer-aided manufacturing zirconia crowns and heat-pressed ceramic veneered zirconia crowns: An in vitro study

Abstract Aim: This study aimed to compare the marginal and internal adaptation of monolithic computer-aided design and computer-aided manufacturing (CAD/CAM) zirconia crowns and heat-pressed ceramic-veneered zirconia crowns fabricated using a standardized digital workflow. Settings and Design: An in vitro laboratory study was conducted using standardized epoxy resin dies and zirconia crowns fabricated by two different laboratory workflows. Materials and Methods: Twenty zirconia crowns were fabricated from a single STL dataset with a 50-µm cement space and divided into two groups ( n = 10): monolithic CAD/CAM zirconia (MZ) and bilayer heat-pressed ceramic-on-zirconia (PVZ). All crowns were fabricated on epoxy resin dies replicated from a CAD/CAM-milled stainless-steel master die. After cementation with glass ionomer cement under a controlled seating load of 50 N, the specimens were sectioned buccolingually. Marginal and internal gaps were measured using scanning electron microscopy at eight predetermined sites. Statistical Analysis Used: Data were evaluated for normality using the Shapiro–Wilk test. Intergroup comparisons were performed using the Mann–Whitney U-test, with statistical significance set at P Results: For the primary outcome, composite internal adaptation was lower in the monolithic CAD/CAM zirconia crown group than in the heat-pressed ceramic-veneered zirconia crown group (103.07 vs. 111.38 µm; P = 0.019), with a moderate effect size ( r = 0.53). Composite marginal adaptation did not differ significantly between the groups (88.90 vs. 95.73 µm; P = 0.226). Conclusion: Both fabrication workflows produced zirconia crowns with marginal and internal adaptations within clinically acceptable limits. Monolithic CAD/CAM zirconia crowns showed slightly smaller internal discrepancies than heat-pressed ceramic-veneered zirconia crowns; however, the magnitude of this difference is unlikely to affect clinical seating or cementation.