Statement of problem: The translucency of cubic zirconia is improved on the expense of its strength. The effect of grinding and finishing on its mechanical properties is still unclear.
Purpose: The aim of this study was to evaluate the influence of glazing and polishing protocols on the surface roughness and flexural strength of monolithic cubic zirconia after dry and wet grinding.
Materials and methods: Super translucent multilayer zirconia (STML) disks were cut, sintered, and glazed according to the manufacturer's recommendations. Samples were randomly divided into three groups according to surface grinding: Group (C): control (no grinding-as glazed), Group (D)grinding under dry condition and group (W) grinding under wet condition. Each group of (D)and(W) was subdivided into two subgroups according to surface finishing whether glazing or polishing. The roughness average (Ra) was measured using contact profilometer. Biaxial flexural strength test was done using a universal testing machine. Statistical analysis was performed.
Results: The glazing showed a statistically significantly higher mean Ra (P<0.05) than polishing whether after wet or dry grinding. The dry ground groups showed a statistically significantly higher mean Ra (P<0.05) than wet ground groups. The glazing showed a statistically significantly lower mean biaxial flexural strength than Polishing (P<0.05) after dry grinding. While there was no statistically significant difference between glazing and polishing (P>0.05) after wet grinding.
Conclusion: Adequate polishing can produce a smoother surface than reglazing. Dry grinding can increase the surface roughness to a degree that can affect the flexural strength of STML zirconia.