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.

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 < 0.05. Bonferroni adjustment was applied for exploratory multiple comparisons.

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.