Bleaching efficacy, decomposition rate and pH of experimental bleaching gels incorporating bioactive materials

Aim: To evaluate the bleaching efficacy, decomposition rate, and pH of experimental gels containing 35% hydrogen peroxide (HP) and different concentrations of 45S5-bioglass (BG) or Biosilicate® (BS). Methods: Bovine enamel/dentin blocks (n=10) were allocated into the groups HP_BG or HP_BS (2.5, 5, 7.5 and 10 wt%) and HP (35% HP – positive control). The blocks were submitted to three sessions of 40 min and 7-day intervals. During the interval, the blocks were kept in artificial saliva at 37ºC. Color change (ΔE00) and whiteness index change (ΔWID) were determined after staining with black tea (T1) and 24 h after the 3rd bleaching session (T2). HP decomposition rate (%) and pH were evaluated for 40 min. Two-way ANOVA and Tukey analyzed ΔE00 and ΔWID data, while the Kruskal-Wallis test determined the decomposition rate and pH of the gels. Results: There were no differences in ΔE00 and ΔWID among the experimental bleaching gels containing BG or BS and 35% HP (p > 0.05), but BG and BS gels displayed lower HP concentration than 35% HP, regardless of the bioactive material concentration (p < 0.05). The experimental BG and BS gels exhibited alkaline pH (ranging from 9.28 to 9.82), which was higher than that of 35% HP (p < 0.05). But regardless of the gel, all kept the pH values stable for 40 min. Conclusion: The experimental gels containing BG and BS did not hamper the 35% HP bleaching efficacy. Moreover, BG or BS gels decreased the hydrogen peroxide concentration and exhibited alkaline pH values.