Durability of resin on bleached dentin treated with antioxidant solutions or lasers

Objective: To assess the influence of antioxidants (sodium ascorbate - SA, epigallocatechin-3-gallate (EGCG) from Camellia sinensis and punicalagin from Punica granatum) or lasers (Er:YAG and diode) on bleached dentin.

Methods: Four hundred and forty slabs of intracoronary dentin were prepared: 224 for bond strength (debonding test) (n = 14), 96 for chemical analysis (EDS) and morphology (SEM) (n = 6), 96 for interface analysis (n = 6) and 24 for atomic force microscopy (AFM). The slabs were distributed according to the post-treatment after bleaching (35% hydrogen peroxide): GI- no bleaching and no post-treatment, GII- only bleached, GIII- 10-days delay in restorative procedure, GIV- 10% SA (10 min), GV- 0.5% EGCG (10 min), GVI- 0.5% punicalagin (10 min), GVII- Er:YAG laser (0.80W, 20s) and GVIII- diode laser (1.5W, 20s). Restorative procedures were done. Half of the slabs were analyzed immediately and the others, after 12 months. Debonding and AFM data were analyzed by ANOVA and Tukey tests (α = 0.05).

Results: All the post-treatments, except for punicalagin, reestablished the immediate bond strength, similar to those restored after 10 days (p > 0.05). Following degradation, EGCG and punicalagin reestablished the bond strength (p < 0.05). Lasers were not effective in maintaining the bond strength after 12 months (p < 0.05). Higher O levels were found after bleaching but were reduced overtime. Ca and P remained stable. SEM and AFM showed residual granules of SA and irregular surface due to the laser action. After aging, tags and good interface were verified in GI, GIII, GV and GVI.

Conclusion: Sodium ascorbate, EGCG or lasers restored the immediate bond strength, but only the natural extracts were effective in the long-term durability of resin. Thus, EGCG at 0.5% for 10 min seems to be the best pre-restorative treatment for bleached substrate.