Illumination-dependent metameric behavior of monolithic zirconia materials

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Illuminant metamerism represents an important consideration in restorative dentistry, as materials that appear color-matched under one light source may differ under another, potentially leading to clinically perceptible shade mismatches. The purpose of this in vitro study was to evaluate the metameric performance of monolithic zirconia materials with different yttrium contents under various illumination conditions using CIEDE2000 (ΔE₀₀) color difference values. Thirty-six square monolithic zirconia specimens (10 × 10 × 0.5 mm) were produced from pre-colored zirconia blocks and divided into 3 groups according to their yttria (Y₂O₃) content: VITA YZ HT, VITA YZ ST, and VITA YZ XT ( n = 12). According to the manufacturer’s specifications, these materials correspond to increasing yttria content ranges of approximately 4–6%, 6–8%, and 8–10% mol%, respectively. To better simulate clinical conditions, a 0.2 mm thick dual polymerized resin cement was prepared using a custom silicone mold. Color measurements were performed with a contact spectrophotometer under 4 different illumination conditions (D65 (reference), D50, F, and A). Color differences between D65 and other illuminators were calculated using the CIEDE2000 formula. Data were analyzed using one-way analysis of variance and Bonferroni post hoc tests ( P < 0.05). Significant differences in ΔE₀₀ values were observed among all zirconia materials under each illumination condition ( P < 0.05). For all groups, the highest ΔE₀₀ values were recorded under A illumination, followed by D50 and F lighting. The ST zirconia material exhibited significantly higher ΔE₀₀ values than the HT and XT materials under all nonreference illumination conditions ( P < 0.05). Under F and D50 illumination, no significant differences were observed between the HT and XT groups ( P > 0.05). The metameric performance of monolithic zirconia materials is significantly influenced by both yttrium concentration and illumination conditions. Evaluating restorations under multiple light sources may enhance esthetic predictability in clinical practice.