Fracture Resistance of Monolithic Glass-Ceramics Versus Bilayered Zirconia-Based Restorations.

PURPOSE: To compare the fracture resistance of monolithic reinforced glass-ceramic restorations with bilayer zirconia-based restorations. MATERIALS AND METHODS: Fifteen ceramic crowns were fabricated on epoxy dies duplicated from a stainless steel master die. They were divided into 3 equal groups (n = 5) according to the type of ceramic material used: group I, monolithic lithium disilicate (IPS e.max CAD), group V, monolithic zirconia-reinforced lithium silicate (Vita Suprinity), and group B (bilayered zirconia substructure with veneering ceramic). All specimens were cemented on epoxy dies with a self-adhesive resin cement (Rely X Unicem), subjected to a chewing simulator, and then loaded until fracture in a universal testing machine. The results were tabulated and statistically analyzed using one-way ANOVA to compare among the 3 materials. The Bonferroni post hoc test was used for pairwise comparisons when the ANOVA test was significant. RESULTS: Zirconia-reinforced lithium silicate (Vita Suprinity) crowns showed the highest statistically significant (p < 0.05) mean fracture resistance values (1742.9 +/- 102.7 N), followed by lithium disilicate (IPS e.max CAD) (1565.2 +/- 89.7 N). Bilayered zirconia-based crowns showed the lowest statistically significantly mean fracture resistance values (1267.8 +/- 86.1 N). CONCLUSIONS: Monolithic reinforced glass-ceramics (lithium disilicate and zirconia-reinforced lithium silicate) have better fracture resistance than bilayered zirconia-based ceramics. CLINICAL IMPLICATIONS: The use of monolithic reinforced ceramic restorations (lithium disilicate and zirconia-reinforced lithium silicate) is preferred to bilayered zirconia-based restorations to avoid chipping of the ceramic veneer.