The effect of smoking on color and translucency of dental zirconia materials manufactured by different methods

Objective: The aim of this study is to compare the color change, translucency, and surface roughness of zirconia fabricated via additive and subtractive manufacturing following cigarette-smoke exposure. Materials and Methods: A total of 60 disk-shaped zirconia specimens (14 × 1 mm) were fabricated using VITA YZ T milling blocks and INNI-CERA (BCM-W500/1000) printing resin. Two groups were formed, each containing 30 specimens. All samples were polished using the OptraGloss zirconia polishing kit. Color coordinates were measured using a spectrophotometer, translucency was assessed using a UV-VIS spectrophotometer, and surface roughness was measured with an optical profilometer. After baseline measurements, the specimens were divided into four subgroups based on exposure condition: Additive-Cigarette, Additive-Saliva, Subtractive-Cigarette, and Subtractive-Saliva. The experimental exposure period lasted for 30 days. Translucency was calculated using the Relative Translucency Parameter (RTP), and color difference was evaluated using the ΔE₀₀ (CIEDE2000) formula. Both calculations were based on CIEDE2000 color difference data. Statistical analyses were performed using Kruskal-Wallis, paired t-test, Wilcoxon, and ANOVA (α=0.05). Results: At baseline, the additive group exhibited significantly lower RTP and surface roughness values compared to the subtractive group (p<0.05). The difference in translucency was not statistically significant (p>0.05). After exposure, RTP significantly decreased in the additive-cigarette group (p<0.05). Translucency values significantly decreased in all groups (p<0.05), while no statistically significant changes were observed in surface roughness. A statistically significant difference in color change was found between the cigarette-exposed additive and subtractive groups (p<0.05), with the additive-cigarette group showing lower ΔE₀₀ values. Conclusion: Additively manufactured zirconia demonstrated better color stability against cigarette exposure with lower initial translucency and surface roughness. However, its translucency property still requires improvement.