Effect of 35% Sodium Ascorbate Treatment on Microtensile Bond Strength after Nonvital Bleaching

Abstract According to previous reports, adverse effects of tooth bleaching on bond strength can be reversed by delaying bonding for 1–3 weeks or by applying 10% sodium ascorbate (SA) for 3 hours or more. This study evaluated the effectiveness of the short-term application of 35% SA to counteract the effects of a 7-day 35% hydrogen peroxide (H 2 O 2 ) bleaching regimen on bond strength. Methods Forty extracted third molars were mounted and sectioned to obtain a flat dentin surface and then randomly assigned into 4 groups: group 1: restored, no bleach; group 2: bleached, bonded immediately; group 3: bleached, treated with two 1- minute 35% SA applications before bonding; and group 4: bleached, treated with two 5-minute 35% SA applications before bonding. For bleach treatment in groups 2–4, flattened dentin surfaces were exposed to H 2 O 2 for 7 days at 37°C. Subsequent to respective treatments, dentin surfaces were built up with composite (TPH3 and Prime &Bond NT, Dentsply Caulk, Milford, DE). After 24 hours of storage (100% humidity, 37°C), the specimens were sectioned into 1-mm 2 dentin-composite beams. Four beams from each tooth ( n = 40/group) were subjected to microtensile bond strength testing. Results Results were as follows: group 1: 18.1 ± 8.1MPa, group 2: 11.3 ± 5.7MPa, group 3: 11.2 ± 5.2MPa, and group 4: 12.6 ± 6.1MPa. A 1-factor analysis of variance and the Tukey post hoc test (α = 0.05) indicated that bleaching had a detrimental effect on bond strength and that short-term SA treatments after bleaching did not significantly improve bond strength. Conclusions The application of 35% SA in a clinically relevant timeframe was not effective at reversing bleaching effects on bond strength. Bonding procedures should be delayed following tooth bleaching.