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 manufacturers 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 understood.

This study aimed to evaluate the effect of sintering temperature on the marginal fit and compressive strength of monolithic zirconia crowns.

In this in vitro study, thirty crowns of pre-sintered monolithic zirconia 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 machine until fracture. One-way ANOVA test was used to analyze the results (α=0.05).

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).

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.