Spectrophotometric evaluation of color changes of Bleachshade resin-based composites after staining and bleaching.Aim: The aim of this study was to evaluate the color stability of two commercially available bleach-shade resin composites (RC) after exposure to 3 storage solutions and the effect of 3 bleaching agents on the color stability and stain removal from stained RC. Materials and methods:Two bleach-shade RC were evaluated in this study, including a nanofilled RC, Filtek TM Z350 XT (FZ), and a nanohybrid RC, Tetric ® N-Ceram (TC), in the extra-white body (shade) (XWB) and L shades, respectively. Twenty-seven disk-shaped specimens, each measuring 12 mm in diameter and 2 mm in thickness, were prepared for each RC, with a total of 54 specimens. Specimens were randomly allocated into 3 groups of 9 specimens each and immersed in 3 storage solutions (distilled water, tea and coffee) for 7 days period. The 9 specimens in each staining group were further divided into 3 subgroups. Specimens in each subgroup (n = 3) were bleached using one of the bleaching agents (10 and 16% Zoom NiteWhite amorphous calcium phosphate (ACP), and Zoom 2 chairside with light activation) for 5 days period. The specimen colors were measured with spectrophotometer. The measurements were performed on each sample three times at baseline, after staining, and after bleaching. Color was expressed using the commission international de I'Eclairage (CIE) L*a*b* color space. The color differences (∆E) between the three measurements were calculated and the results were statistically analyzed using Two-way and Three-way analysis of variance (ANOVA) and Tukey's posthoc tests. Level of significance was set at p < 0.05. Results: Tetric® N-ceram materials demonstrated significantly less color change than the FZ and the color change, which was greater after storage in coffee compared to tea, was statistically significant. The bleaching agents significantly influence the color changes of composite specimens. All groups showed (∆E) values below 3.3 after bleaching, except for 'Zoom 2 chairside' with light activation groups, which is shown clinically unacceptable lighter shade (ΔE >3.3). Conclusion: Bleach-shade composites showed significant discoloration (ΔE > 3.3) after being immersed into coffee and tea solutions. Nanofilled composites discolored more than nanohybrid composites, and carbamide peroxide-based bleaching agents were effective in reducing the discoloration to a clinically acceptable value (∆E > 3.3). ORIGINAL RESEARCHClinical significance: In this study, after clinically significant discoloration, low concentrations of carbamide peroxide bleaching agents were effective in removing stains and restoring the color of bleach-shade composites to near baseline color.