Objective: To assess the effect of different antioxidant agents on surface roughness, ultra-morphology, and microtensile bond-strengths (µTBS) to bleached dentin. Methods: 18 freshly extracted third molars were selected and randomly assigned to 6 groups (n=6): (NB) dentin not bleached, (B) bleached dentin, (BR7) bleached dentin and restored 7 days later, (BSA) bleached dentin+sodium ascorbate, (BCT) bleached dentin+catalase, (BPX) bleached dentin+peroxidase. 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<.05). Nineteen third molars were selected and processed for AFM and FESEM. The mean dentin roughness (n=9) and ultra-morphology (n=2) were evaluated in different periods: 1) before the bleaching, 2) after the bleaching, and 3) after the application of the antioxidant agents. A 1-way ANOVA/Tukey post-hoc test (P<.05) was computed. Results: The hydrogen peroxide and all antioxidant agents, mainly sodium ascorbate, increased significantly dentin roughness (P<.0001). Smear layer was not removed after application of different treatments. (Mean and SD in MPa, PTF = pre-testing failures/ spontaneous debonding, and N = number of specimens):
24 Hours | Groups | Aged | ||||
Mean (SD) | PTF | N | N | PTF | Mean (SD) | |
79.9 (18.7)A | 0 | 40 | NB | 48 | 4 | 65.5 (29.7) A |
0.0 (0.0) B | 43 | 43 | B | 40 | 40 | 0.0 (0.0) B |
63.7 (27.2) A | 4 | 61 | BR7 | 39 | 7 | 51.0 (27.8) A |
2.8 (8.0) B | 55 | 64 | BSA | 44 | 42 | 1.5 (7.2) B |
1.1 (4.4) B | 45 | 48 | BCT | 54 | 54 | 0.0 (0.0) B |
1.9 (6.2) B | 39 | 43 | BPX | 44 | 44 | 0.0 (0.0) B |
Conclusion: Antioxidant agents were not effective in reversing bond strengths of bleached dentin. Bleached dentin can be effectively restored 7 days post-bleaching.
CAPES: 1578-08-1