Statement of problem. Occlusal cement space thickness (OST) affects the marginal and internal fit of ceramic crown. However, the recommendations for vertiprep OST settings for ceramic crowns are limited.
Purpose. The purpose of this study was to evaluate the marginal and internal fit of zirconia and hybrid ceramic crowns restoring verti-preped premolars, designed with different OST.
Materials and Methods. Upper premolar typodont was prepared with an edgeless finish line. A standardized crown design with 70μm axial cement space thickness was created using EXOCAD software. 40 crowns were grouped: Groups Z50 and Z70 for monolithic zirconia crowns with 50μm and 70μm OST respectively, and Groups En50 and En70 for hybrid ceramic crowns with the same OST settings (n = 10). All crowns were produced following manufacturers' instructions. Vertical marginal gap (VMG) and internal gap (IG) were assessed using direct viewing and silicone replica techniques respectively, under a stereomicroscope. Statistical analysis included one-way ANOVA followed by Tukey's post-hoc test for group and site comparisons (P ≤ 0.05).
Results. En70 showed the lowest VMG values, followed by En50, Z70, and Z50. Z70 showed the lowest IG values, followed by Z50, En50 and En70. The occlusal surface exhibited the highest gap values in all groups, while the cervical area showed the least values.
Conclusions. The OST and the ceramic crown material had a significant effect on the marginal and internal fit of the final crown. The recommended OST for zirconia crowns is 70 μm, whereas for hybrid ceramic crowns, 50 μm is preferred.