The Effect of Glazing, Reglazing, and Polishing on Zirconia Biaxial Flexural Strength

Zirconia restorations are usually coated with glazing to provide an aesthetic and reduce wear on opposing teeth. Occlusal adjustments such as grinding and polishing to eliminate occlusal or internal interferences can affect the mechanical properties of zirconia. The purpose of this study was to evaluate the effect of glazing, reglazing, and polishing procedures on the biaxial flexural strength of zirconia ceramic. This experimental study used 20 samples of zirconia discs (12x1,2 mm), which were divided into fourth groups (n=5). The first group was zirconia discs without treatment as control, the second group with glazing treatment, the third group with reglazing treatment, and the fourth group with polishing treatment. Biaxial flexural strength was determined using a piston on three balls technique. The data were analyzed using 1-way ANOVA and t-test. The results of this study showed no statistically significant difference between the group with glazing, reglazing, polishing and the control group (p>0.05). The highest zirconia biaxial flexural strength was found in the polished group but not significant statistically (1913.64 ± 594.28 MPa). The reglazing group with the lowest average biaxial flexural strength was (1413.01 ± 365.66 MPa). It can be concluded that there were no differences in biaxial flexural strength between the polishing, glazing, and reglazing group. The use of polishing can be an alternative technique to improve aesthetics besides glazing and reglazing because it does not impair the biaxial flexural strength of zirconia.