Abstract
BACKGROUND: This study aimed to evaluate the long-term color stability of single-shade composite resins when exposed to simulated intraoral conditions, including staining, brushing, and thermal cycling. Additionally, the study compared the performance of spectrophotometry and cross-polarized (CP) photography in detecting color changes, focusing on their applicability for both clinical and research purposes. MATERIALS AND METHODS: The study employed five single-shade composite resins (Omnichroma; OMN, Zenchroma; ZNC, Vittra APS Unique; VTR, Charisma One; CHR, and Essentia Universal; ESU) and one multi-shade composite resin (Filtek Z550: FLT) for testing. The specimens were subjected to thermal cycling, staining, and brushing to simulate intraoral conditions. Color measurements were conducted using a spectrophotometer and CP photography at the initial baseline (t(0)) and following each subsequent procedure 10-day (t(1)) and 1-year simulated staining, brushing and thermal cycling (t(2)). Color differences (ΔE(1), ΔE(2)) were calculated using the CIEDE2000 formula. Statistical analyses included Shapiro-Wilk for normality, ANOVA and paired t-tests for parametric data, and Kruskal-Wallis and Wilcoxon tests for non-parametric data. Method consistency was evaluated with the Intra-Class Correlation Coefficient (ICC) (p < 0.05). RESULTS: All composite groups demonstrated statistically significant color changes following the simulated conditions (p < 0.001). The CHR group exhibited the highest values for both ΔE(1) and ΔE(2), indicating the greatest degree of discoloration. The FLT and ZNC groups exhibited the lowest ΔE values across methods at various time points. A positive correlation was identified between spectrophotometer and CP photography measurements for all parameters (p < 0.001), although the correlation for ΔE(1) and ΔE(2) was less robust. CONCLUSIONS: Single-shade composites display a high susceptibility to significant discoloration when subjected to simulated intraoral conditions, with CHR exhibiting the most pronounced alterations. Both spectrophotometry and CP photography were effective in assessing color stability, with CP photography offering a practical alternative for clinical settings. These findings offer insight into the aesthetic durability of single-shade composites and underscore the importance of long-term evaluations.