Effect of Fabrication Stages and Cementation on the Marginal Fit of CAD/CAM Monolithic Zirconia Crowns

Objectives: The purpose of this in vitro study was to evaluate the effect of different stages of fabrication and cementation on the vertical marginal discrepancy (VMD) of CAD/CAM fabricated monolithic zirconia crowns.
Methods: Six ivorine right maxillary first molar typodont teeth with standardized anatomic preparations for complete-coverage ceramic crowns were scanned with a 3-dimensional laboratory scanner. Crowns were designed using a CAD software and milled from presintered monolithic zirconia blocks in a 5-axis dental milling machine. A cement space of 25 µm for the margins and 50 µm space starting 1 mm above the finish lines of the teeth was virtually set in the CAD software. A total of 144 measurements under a stereoscopic zoom microscope were performed on 6 specimens with 8 measurement locations in 3 different stages; after initial production of the crowns (post-Sintering Group - S), after glazing (post-Glazing Group - G), and after cementation (post-Cementation Group - C). The VMD values were statistically analyzed with 1-way repeated measures ANOVA and Holm-Sidak method (α=.05).
Results: Different stages of fabrication and cementation significantly affected the VMD of tested crowns (P=.003). Mean VMD was 38 µm for group S, 38 µm for group G, and 60 µm for group C, with statistical difference between groups S and C (P=.017) and groups G and C (P=.025), and no statistical difference between groups S and G (P=.050).
Conclusions: Within the limitations of this study, glazing did not significantly change the VMD of CAD/CAM monolithic zirconia crowns. Cementation significantly increased the VMD values. Simulated cement space can be set at 50 µm for clinically acceptable marginal fit of CAD/CAM monolithic zirconia crowns in the molar region when tested cement is used for cementation.