Impact of Calcium Hydroxide, Sodium Ascorbate, and Sodium Thiosulfate on the Bond Strength of Composite Restorations to Bleached Dentin

This study evaluated the impact of using calcium hydroxide or antioxidant agents on the bond strength of adhesive restorations to bleached dentin. A total of 40 teeth were prepared and allocated into eight groups, first divided according to the surface treatment after bleaching (no treatment or application of calcium hydroxide, 10% sodium ascorbate, or 5% sodium thiosulfate for 10 minutes) and then according to the time of final restoration after treatment (immediate or after 7 days). Sodium perborate with 20% hydrogen peroxide was applied for 3 weeks using a developed artificial pulp chamber, with peroxide replacements provided every week. Composite resin restoration was performed, followed by a microtensile test. Then, specimens were analyzed using a stereomicroscope and scanning electron microscopy (SEM). Data were submitted to Kruskal-Wallis and Dunn tests (P < .05). The bond strength of nonbleached teeth was similar to the groups restored after 7 days of bleaching (P < .05). The lowest bond strength values were seen in groups restored immediately after bleaching (P < .05). In all groups, there was a considerable predominance of adhesive fractures. Delaying the final restoration of teeth submitted to nonvital bleaching by 7 days increased the bond strength. The immediate restoration of bleached teeth after using 10% sodium ascorbate or 5% sodium thiosulfate for 10 minutes showed unsatisfactory results. Irrespective of the dentin protocol applied before adhesion, bond strength values will be satisfactory when delaying the final restoration and unsatisfactory when immediately performing the final restoration. Therefore, after nonvital tooth bleaching, clinicians should always delay the final restoration for a minimum period of 7 days.