Optical properties and color stability of a translucent zirconia: effects of finishing after grinding.

Abstract

This study evaluated the effect of grinding and finishing treatments (polishing or glaze) on the color stability, translucency and opalescence of a translucent zirconia (3Y-TZP) after immersion in red wine. Discs (Ø= 12 mm; thickness 0.8 mm) of 3Y-TZP (Zenostar T, Ivoclar AG) were randomly allocated (n= 8) according to the surface treatment factor: Ctrl - as-sintered; Gr - grinding with diamond bur #4219; Gr + Pol - grinding followed by polishing; Gr + Gl - grinding followed by glaze. Surface roughness and scanning electron microscopy were carried out. All specimens were subjected to daily immersions in red wine for 30 minutes during 18 days. The color differences (ΔE00) were measured prior, after 9 and 18 days of immersion through the CIEDE2000 formula, as same as translucency (TP00) and opalescence (OP) parameters. Kruskal Wallis, repeated measures ANOVA/Tukey, and Spearman's correlation tests were performed to evaluate the roughness, optical and correlation data, respectively. The Gr + Gl depicted the lowest ΔE00 value after 9 days. The Gr group showed the greatest ΔE00 values in all immersion times, whereas the other groups presented similar behavior after 18 days. The Gr and Gr + Pol groups had the highest Ra and Rz values. The correlation between roughness and color change was moderate and significant (p= 0.02, r= 0.42). No differences were observed for TP00 and OP. The surface treatments affected the roughness and color stability of zirconia, being glaze application more effective to reduce color alterations after the immersion protocol.