Effect of Finishing Protocol Treatments on Optical Properties of Super Translucent Zirconia After Simulated Wear

TL;DR

This study shows that different finishing methods affect how super translucent zirconia maintains its color and translucency after simulated toothbrushing.

Contribution

The study introduces a novel comparison of three finishing protocols on the optical stability of super translucent zirconia under simulated wear.

Findings

Chroma + Glaze treatment resulted in the lowest translucency and highest color stability after simulated brushing.

Polished zirconia showed increased translucency and greater color changes after wear.

Color changes in the Chroma + Glaze group remained below perceptibility thresholds.

Abstract

Background/Objectives: Super translucent zirconia (ST zirconia) is increasingly used for esthetic restorations, but its optical stability after mechanical wear remains unclear. This study aimed to evaluate the effects of three finishing protocols—polishing, glazing, and staining followed by glazing (Chroma + Glaze)—on the color stability and translucency of ST zirconia after simulated toothbrushing. Methods: Sixty zirconia specimens (Vita YZ ST, shade A1) were fabricated and divided into three groups, namely Polished, Glazed, and Chroma + Glaze (n = 20 in each group). Color (L*, a*, b*) was measured using a spectrophotometer (VITA Easyshade V; VITA Zahnfabrik) before and after 10,000 brushing cycles (200 g load, 1.5 Hz). Translucency parameters (TPab, TP00) were calculated, while color changes were assessed using CIELAB (ΔEab) and CIEDE2000 (ΔE00) formulas. Data were analyzed using two-way ANOVA and Kruskal–Wallis tests (α = 0.05). Results: Treatment significantly affected translucency (H = 46.79, p < 0.001; H = 21.09, p < 0.001), indicating consistent differences among the three treatment groups. Bonferroni-adjusted post hoc comparisons showed that Chroma + Glaze exhibited significantly lower TP00 values than Glaze in both measurements (p < 0.0001; p < 0.001), as well as lower values than Polished in both measurements (p < 0.0001; p = 0.0147, respectively). Kruskal–Wallis analysis revealed significant differences among finishing protocol groups for both ΔEab (H = 13.21, p < 0.0014) and ΔE00 (H = 9.14, p = 0.0104), with Chroma + Glaze exhibiting the smallest ΔE values (ΔE00 ≈ 0.33) below the perceptibility threshold. Conclusions: The finishing protocol significantly influences the optical behavior of ST zirconia after simulated wear. The Chroma + Glaze group demonstrated the highest color stability and lowest translucency, suggesting enhanced long-term esthetic performance. In contrast, polished zirconia showed greater color variation and an increase in translucency, indicating lower optical stability under brushing abrasion.

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