Color Stability and Color Recovery of Single-shade Restorative Resin Composites: An In-Vitro Study

Introduction Single-shade restorative resin composites simplify shade selection, but their color stability and response to whitening mouthrinses remain uncertain. This in-vitro study evaluated their staining susceptibility and subsequent color response. Materials and Methods A total of 360 specimens (6 × 2 mm) were prepared from three single-shade restorative resin composites and one nanohybrid control. Specimens were immersed in distilled water, coffee, or red wine for 1 month (n = 30). They then underwent a 4-week protocol using one of two peroxide-free whitening mouthrinses (n = 15). Color was measured three times with a spectrophotometer at baseline, after immersion, and after mouthrinse application. CIEDE2000 color differences were analyzed using analysis of variance and multiple linear regression ( p < 0.05). Results Material and immersion medium significantly affected color change ( p < 0.001). At 1 month, red wine caused the greatest change (12.74 ± 2.50 to 21.53 ± 1.99), followed by coffee (7.80 ± 2.35 to 13.88 ± 2.27); distilled water produced the lowest values. The response to mouthrinse application varied by material and medium. Residual color difference decreased in most red-wine groups but increased in some distilled-water and coffee groups. Complete color recovery was not achieved. Discussion CDO was the most susceptible material, whereas OMN and ESQ were more resistant. Reduced lightness was the predominant component of staining. Conclusion Staining and the response to mouthrinse application were material- and medium-dependent. Peroxide-free mouthrinses did not consistently reduce residual color differences across all experimental groups.