Marginal Accuracy of Monolithic Zirconia Crowns with Vertical and Horizontal Margin Configurations after Thermomechanical Fatigue

Purpose: The aim of this study was to evaluate the effect of two types of finish line designs on the marginal accuracy of monolithic zirconia crowns after thermomechanical fatigue. Materials and Methods: two human first molars were prepared and duplicated using epoxy resin to produce twenty dies. Accordingly, a total of 20 monolithic zirconia crowns (N=20) were designed and constructed using CAD/ CAM machine. The crowns were divided into two groups according to the finish line design, feather edge (FE) group (n=10) and deep chamfer (DC) group (n=10). All crowns were adhesively bonded to their corresponding epoxy resin dies by using dual cure self-adhesive resin cement and subjected to thermo-mechanical fatigue simulating 3 months of clinical situations then vertical marginal gap was measured using digital microscope. Results: Statistical analysis showed that deep chamfer margin design recorded statistically significant higher marginal gap mean value (39.6383 ± 5.00193 μm) than feather edge design (32.2616 ± 2.60053μm). Conclusion: marginal accuracy of monolithic zirconia constructed with feather edge margins is better than that with deep chamfer margin designs.