Preventive effects of whitening mouthrinses against coffee-induced discoloration in different types of resin composites: a daily-use in-vitro study

This in vitro study aimed to evaluate the preventive effects of whitening mouthrinses against coffee-induced discoloration and to assess their influence on the optical properties-color difference (ΔE₀₀), translucency parameter (ΔTP), and whiteness index difference (ΔWID)-of different resin composite materials. Three resin composites were tested: Filtek One Bulk Fill (FOB), Charisma Diamond One (CDO), and Estellite Sigma Quick (ESQ). Specimens were immersed daily in coffee, followed by exposure to three whitening mouthrinses-Listerine Advanced White (LAW), Colgate Optic White (COW), and R.O.C.S. Whitening Mouthrinse (ROC)-for 3 months. Distilled water served as the negative control. Color measurements were conducted with a spectrophotometer on standardized black, white, and gray backgrounds. ΔE₀₀ values were analyzed using mixed-design ANOVA or Kruskal-Wallis tests depending on data distribution, while ΔTP and ΔWID values were evaluated using appropriate non-parametric tests (p < 0.05). All whitening mouthrinses significantly reduced coffee-induced discoloration (p < 0.05). LAW and COW, both containing hydrogen peroxide, exhibited the lowest ΔE₀₀ values (≈ 2.0-2.3), while ROC showed limited efficacy. Whitening mouthrinses did not significantly affect translucency (ΔTP) values (p > 0.05), whereas coffee exposure resulted in a statistically significant reduction in translucency. Whitening rinses produced a mild increase in whiteness (ΔWID ≈ + 1.0- + 1.6), below the clinical perceptibility threshold (ΔWID ≥ + 2.0). Among materials, the nanohybrid composite ESQ demonstrated the most stable optical behavior across all parameters. Hydrogen peroxide-containing whitening mouthrinses exerted a preventive effect against coffee-induced discoloration without producing clinically perceptible whitening, thereby helping to maintain the optical stability of composite restorations.