Color stability of bleached enamel after treatment with CPP-ACP, S-PRG, and sodium fluoride

The aim of this study was to evaluate the color stability of bleached teeth after treatment with bioactive materials. Forty bovine teeth underwent four 45-minute bleaching sessions with 35% hydrogen peroxide (Whiteness HP, FGM), followed by application of the respective remineralizing agent after each bleaching session. After the final session, the specimens were randomly assigned (n = 10) to one of the following treatments: control (without gel), casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) gel (MI Paste, GC Brasil), S-PRG-based gel (PRG Pro Care Gel, Shofu), or 2% sodium fluoride gel (NaF-Maquira), applied according to the manufacturers' instructions. The specimens were then immersed in a coffee solution three times daily for 15 minutes over 14 days. Color measurements were performed using a spectrophotometer, evaluating Vita classical shade guide and CIELab* parameters at baseline, after bleaching, and after staining. Data were analyzed using generalized linear mixed models for repeated measures, as well as Friedman, Nemenyi, and Kruskal-Wallis tests (α = 5%). Bleaching significantly increased L* and Whiteness Index for Dentistry (WID) values and reduced a* and b* values (p < 0.05). After staining, L* and WID decreased, while a* and b* increased significantly (p < 0.05). Compared to baseline, sodium fluoride and S-PRG groups showed higher ΔEab and ΔE00 values than the control (p < 0.05). After coffee staining, no differences among groups were found for ΔE*ab, ΔE00, or ΔWID, indicating that none of the bioactive gels altered the susceptibility of bleached enamel to coffee-induced color change.