Effect of Over-the-Counter Whitening Dentifrices on the Color Stability and Microhardness of Composite Resins

Objective: To evaluate the color stability and microhardness of resin-based bioactive composites after brushing with over-the-counter whitening toothpastes. Methods: A conventional resin (Luna 2) and two bioactive resins (Stela Mix and Activa Presto) were tested. Four toothpastes were used: Colgate Fresh Gel (control), Colgate Max White, Yotuel, and Crest 3D White. Forty disks of each material were prepared and divided into four subgroups. The disks were brushed to simulate three months of daily brushing. Microhardness and color changes were measured before and after brushing. Color variation was calculated using the ΔEab, ΔE00, and ΔWID indexes. Wilcoxon and two-way ANOVA tests were performed (p < 0.05). Results: In the Luna 2 and Stela groups, the b* parameter decreased significantly with all toothpastes (p < 0.05), while lightness and a* remained stable with no significant differences (p > 0.05). Stela Mix and Activa Presto exhibited color changes within the “moderately unacceptable” range according to ΔE00 (>1.8 and ≤3.6). Based on the ΔWID index, Luna 2 showed the highest variation when treated with Colgate Max (2.14 ± 1.33) and the lowest in the control group (1.08 ± 0.56A), remaining within acceptable margins with all treatments. The microhardness values before/after treatment remained for Luna 2 between 77.44 and 76.97; for Stela Mix between 76.24 and 74.13; and for Activa presto between 74.5 and 71.33. Differences were not significant for any of the pastes within each composite (p > 0.05). Conclusions: The evaluated bioactive resins exhibited color changes within the moderately unacceptable range. Colgate Max White induced the most significant color changes. Microhardness was not affected by treatment with whitening toothpastes.