Long Term Evaluation of Antioxidants Agents on Bleached Enamel

Objective: To assess the effect of different antioxidants agents on surface roughness, ultra-morphology, and microtensile bond-strengths (µTBS) to bleached enamel. Methods: 36 freshly extracted third molars were selected and randomly assigned to 6 groups (n=6): (NB) enamel not bleached, (B) bleached enamel, (BR7) bleached enamel and restored 7 days later, (BSA) bleached enamel+sodium ascorbate, (BCT) bleached enamel+catalase, (BPX) bleached enamel+peroxidase. All groups were bleached with 38% hydrogen peroxide (Opalescence Xtra Boost) and restored with Single Bond+Filtek Z250. The specimens were tested after 24 hours and after artificial aging (20,000 thermal cycles and 1,200,000 mechanical loading cycles). The data were submitted to Kruskal-Wallis analysis followed by multiple comparisons (p=0.05). Additionally, 15 extracted central incisors were selected and processed for AFM and FESEM. The mean enamel roughness (n=3) and ultra-morphology (n=2) were evaluated in three different periods: 1) before the bleaching, 2) after the bleaching, and 3) after the application of the antioxidants agents. A 1-way ANOVA/Tukey post-hoc test at p=0.05 was computed. Results: Peroxidase increased significantly enamel roughness (p<.0001). A mild etching pattern was observed after bleaching and after the application of antioxidants. (Mean and SD in MPa, PTF = pre-testing failures/ spontaneous debonding, and N = number of specimens):

Conclusion: Antioxidants agents were not effective in reversing bond strengths of bleached enamel. Bleached enamel can be effectively restored 7 days post-bleaching.