Effects of high‐speed sintering on the translucency and color of dental zirconia with different shades and yttria contents

Purpose This study evaluated the effects of high‐speed sintering on the translucency and color of various yttria‐stabilized zirconia (YSZ) compositions and identified factors influencing these properties to improve clinical predictability. Materials and Methods A total of 144 disc‐shaped specimens fabricated from 3YSZ, 4YSZ, and 5YSZ pucks in shades B1, A3, and C4 were sintered using conventional (∼12 h) or high‐speed (∼18 min) protocols. Specimens were polished to a 0.5 µm finish and measured Ø 13.75 mm × 1 mm. Porosity, phase content, translucency, color, and elemental composition were quantified ( n = 8). Normality was assessed using the Shapiro–Wilk test. Pairwise comparisons were performed using Wilcoxon rank‐sum tests where appropriate. The effects of shade, yttria content, sintering protocol, and their interactions were evaluated using factorial ANOVA ( α = 0.05). Results High‐speed significantly reduced translucency and diminished the translucency advantage of 5YSZ, particularly in darker shades. The reduced translucency was attributed to increased porosity. High‐speed also produced lighter specimens (higher L * values) with lower a * and b * values, indicating a shift toward greener, less yellow color coordinates. Color differences (Δ E 00 ) were greatest in C4‐shaded specimens. Additionally, a distinct light–dark subgrouping was observed within the 4YSZ‐B1 high‐speed condition. Compositional analysis showed that HS reduced Fe 2 O 3 levels while maintaining NiO, suggesting that color changes may be associated with Fe 2 O 3 instability and increased porosity. Conclusions High‐speed reduced translucency and altered clinically perceptible color in dental zirconia, especially in high‐yttria contents and darker shades.