Effect of Glazing on Flexural Strength of Full-Contour Zirconia.

Objective: The purpose of this study was to evaluate the effect of glazing on flexural strength of highly translucent zirconia materials.

Materials and Methods: Specimens of three brands of zirconia bars (Prettau Zirconia, Zirkonzahn; inCoris TZI, Sirona; and Zirlux FC, Pentron Ceramics) were prepared and polished according to manufacturers' instructions. Final specimen dimensions were 20 × 4 × 2 mm. The specimens from each brand were divided into 3 groups ( N  = 10): control, heat-treated, and glazed. Heat-treated specimens were fired without the application of the glaze material. The glaze material was applied to the glazed specimens before being fired. A three-point bending test (15 mm span) was performed in an Instron universal testing machine (ISO 6872). Data were analyzed by ANOVA and Tukey's HSD post hoc test ( α  = 0.05).

Results: Two-way ANOVA showed a significant influence of surface treatments on flexural strength of zirconia materials ( P ≤ 0.05). There was no significant difference in flexural strength among the different brands of highly translucent zirconia ( P ≥ 0.05). Tukey's HSD post hoc test showed that specimens in the "glazed" group had significantly lower flexural strength than the control and heat-treated groups ( P ≤ 0.05).

Conclusion: Within the limitations of the study, external glazing decreased the flexural strength of highly translucent zirconia.