Effect of Grinding and Subsequent Various Surface Treatments on the Surface Roughness of Full Contour Monolithic Zirconia

BACKGROUND A smooth zirconia surface is necessary to protect the opposing natural dentition, to prevent plaque accumulation and to increase the survival rate of restoration by reducing the chances of failure by crack propagation. Surface roughness can be incorporated by routine dental procedures done in labs and clinics to adjust the restoration. It is unclear which surface treatment is most appropriate to achieve clinically acceptable zirconia surface. The purpose of this study was to evaluate the effect of grinding and subsequent various surface treatments on the surface roughness of full contour monolithic zirconia. METHODS In this invitro study 10 zirconia bars of final dimensions 20 x 4 x 2 mm & 40 zirconia bars of final dimensions 20 x 4 x 2.2 mm were milled and sintered. The zirconia bars with final dimensions 20 x 4 x 2mm were glazed and selected as samples for control group (Group C) (n = 10). Forty zirconia bars with dimensions of 20 x 4 x 2.2 mm were grounded using a standard straight cylindrical diamond point (105 – 125 µm) by placing them in a customized grinding apparatus till the dimensions became similar to that of control group i.e. 20 x 4 x 2 mm. After grinding and confirming the dimensions of each full contour monolithic zirconia bar using digital vernier caliper, zirconia bars were randomly allocated into 4 groups with 10 samples in each group (n = 10), namely (Group G: Grinding only, Group G+R: Grinding & Reheating, Group G+G: Grinding & Glazing, Group G+P: Grinding & Polishing) respectively. Surface roughness values were measured using a profilometer. Differences between groups were examined using one-way analysis of variance (ANOVA) (P ≤ 0.05) and Post hoc Tukey HSD test was done for multiple comparisons of surface roughness in between the groups using Statistical Package for Social Sciences (SPSS) software. RESULTS Group C showed the least surface roughness values. The maximum surface roughness values were seen in Group G. Surface roughness of Group G, Group G + H and Group G + G were statistically significant from Group C and Group G + P. There was no statistically significant difference in surface roughness values between Group C and Group G + P. CONCLUSIONS It can be concluded that polishing after grinding significantly reduced the surface roughness and re-established the surface smoothness of full-contour monolithic zirconia bars. KEY WORDS Surface Roughness, Zirconia, Monolithic, Full Contour, Profilometer