Influence of Sintering Temperature on the Marginal Fit and Compressive Strength of Monolithic Zirconia Crowns

Statement of the Problem: Increasing the sintering temperature is suggested by some man-ufacturers as a way to enhance the translucency of monolithic zirconia crowns. Meanwhile, its effect on the marginal fit and compressive strength of the restoration is not fully under-stood. Purpose: This study aimed to evaluate the effect of sintering temperature on the marginal fit and compressive strength of monolithic zirconia crowns. Materials and Method: In this in vitro study, thirty crowns of pre-sintered monolithic zir-conia were milled and sintered in a special furnace at either 1450°C or 1550°C (n=15 per group). The marginal gaps were measured at 18 spots on the dies with a digital microscope. To evaluate the compressive strength, the specimens were cemented on brass dies by using conventional glass ionomer cement. Vertical load was applied by a universal testing ma-chine until fracture. One-way ANOVA test was used to analyze the results (α=0.05). Results: The marginal gap was not significantly different between the two groups (p= 0.062). A significantly higher mean value of compressive strength was observed in crowns sintered at 1550°c (1988.27±635.09 N) than those sintered at 1450 °c (1514.27±455.11 N) (p= 0.026). Conclusion: Although increasing the sintering temperature would not affect the marginal gap of monolithic zirconia crowns, it could significantly improve the compressive strength of zirconia restorations.