EFFECT OF VENEERING PORCELAIN THICKNESS AND BACKGROUND SUBSTRATE ON THE COLOR MATCHING OF ZIRCONIA-BASED RESTORATIONS: AN IN-VITRO STUDY

Abstract

Objective: Zirconia-based restorations are increasingly used in esthetic dentistry due to their mechanical strength and favorable optical properties. However, challenges in achieving accurate color matching remain, particularly due to the influence of veneering porcelain thickness and background shade. This study aimed to evaluate the effect of these two variables on the final color of zirconia restorations. Materials and methods: This in vitro study evaluated 33 zirconia discs (A2 shade, 0.5 mm thick), each veneered with porcelain to final thicknesses of 0.8 mm, 1.0 mm, or 1.2 mm (n = 11 per group). Each specimen was measured over three background materials: composite resin, titanium, and nickel–chromium. CIELAB coordinates were recorded using a colorimeter, and color differences (ΔE₀₀) relative to the VITA reference shade were calculated using the CIEDE2000 formula. Data were analyzed using two-way repeated-measures ANOVA followed by Tukey’s post hoc test. Results: Both porcelain thickness and background shade significantly affected L*, a*, and ΔE₀₀ values (p < 0.01). Thickness had no significant effect on b* values, while background shade did. The 1.0 mm porcelain group achieved the most favorable ΔE₀₀ values across all backgrounds, with titanium consistently yielding the poorest color match. Conclusion: Porcelain thickness and background shade significantly influence the final color of zirconia restorations. A veneering thickness of 1.0 mm provided the most acceptable shade matching, particularly over composite and Ni-Cr substrates. These findings underscore the importance of optimizing both material layering and background management in clinical practice.