Color Change and Cytotoxic Effects of a Bleaching Gel With 22% Carbamide Peroxide Catalyzed by Manganese Oxide.

OBJECTIVES: To evaluate the color change and trans-amelodentinal cytotoxicity of a 22% carbamide peroxide (CP) bleaching gel containing different concentration of manganese oxide (MnO(2)). MATERIAL AND METHODS: Enamel/dentin discs adapted to artificial pulp chambers were distributed according to treatments: CN-No treatment; CP22%-22%CP; CP22 + 2MnO(2)-22%CP + 2 mg/mLMnO(2); CP22% + 6MnO(2)-22%CP + 6 mg/mLMnO(2); CP22% + 10MnO(2)-22%CP + 10 mg/mLMnO(2) applied for 2 h for 15 days. Color change-CC (DeltaE(00) and DeltaWI(D)) (n = 8) was determined at 5, 10, and 15-day periods (ANOVA/Sidak). Trans-amelodentinal cytotoxicity (TC) was assessed after applying the extracts to cultured MDPC-23 cells, which were analyzed concerning their viability (Vi) (n = 8) and oxidative stress (OxS) (n = 8). The amount of hydroxyl radical (OH(*)) (n = 4) generated by H(2)O(2) degradation (ANOVA/Sidak), and trans-amelodentinal diffusion of H(2)O(2) (n = 8) (ANOVA/Tukey) were also evaluated. RESULTS: CP22 + 10MnO(2) presented higher CC than CP22 for both evaluated equations in all analysis periods (p </= 0.04). Among bleached groups, CP22 + 10MnO(2) presented the highest OH(*) generation (p </= 0.02) and the lowest trans-amelodentinal diffusion of H(2)O(2) (p </= 0.0004). Therefore, MDPC-23 cells in CP22 + 10MnO(2) exhibited the lowest OxS (p < 0.0001) and consequently the highest Vi (p </= 0.0146). CONCLUSION: Besides increasing the bleaching efficacy, the strategy of adding 10 mg/mL of MnO(2) to a 22%CP bleaching gel also reduces significantly the trans-amelodentinal diffusion of H(2)O(2), diminishing the cytotoxicity caused by at-home bleaching therapy. CLINICAL SIGNIFICANCE: The addition of MnO(2) to a 22% carbamide peroxide bleaching gel improves the color change and reduces the cytotoxicity effects of the product, making at-home bleaching faster and biologically safer.