In vitro evaluation of the polishing effect and optical properties of monolithic zirconia

The relationship between surface roughness and the optical characteristics of zirconia prostheses may be affected by the type of shaded block.The purpose of this in vitro study was to investigate changes in surface roughness and brightness of monolithic zirconia blocks of different shades after polishing.The surface roughness averages of 3 different kinds of shaded zirconia blocks (Zenostarof T0 [T0], Zenostar sun [Ts], and Zenostar sun chroma [Tsc]) were compared after surface polishing. Fifteen specimens of differing thicknesses were produced per block. (1 mm and 3 mm). Surface morphology and compositions were analyzed by using filed emission scanning electron microscopy (FE-SEM) and energy dispersive spectrometry. A 1-way ANOVA and the post hoc Scheffé test were performed (α=.05). The correlations between surface roughness and brightness were determined using the Pearson correlation analysis (α=.01).After phased polishing, Ts had the highest average roughness, followed by T0 and then Tsc. A statistically significant difference in roughness was observed between Ts and Tsc (P.05). Ts exhibited multiple distinct layers in the FE-SEM image. Carbon was detected in the Ts specimens only. Brightness was highest in T0, followed by Ts and then Tsc. A positive correlation was observed between brightness and surface roughness for all specimens (P.01). This correlation was stronger in the thicker specimens.The results of this study suggest that polishing affects monolithic zirconia differently depending on shade. The polishing of monolithic zirconia reduces both surface roughness and brightness. The optical properties of monolithic zirconia vary by thickness and can be opaque or translucent.