A recent study evaluated the influence of various time intervals after tooth bleaching with 35% hydrogen peroxide on the bond strength of resin-based com­posite re­storations. Bitten­court, et al published their findings in the March issue of the Jour­nal of the American Dental Associa­tion. 

This study in­volved 20 subjects; enamel and dentin blocks were randomly fixed onto the buccal surfaces of posterior maxillary teeth one week prior to bleaching the teeth with 35% hydrogen peroxide. After bleaching, one block of dentin or enamel was re­moved and prepared for bond strength tests according to these time intervals: no bleaching treatment (controls), immediately after bleaching, 7 days after bleach­ing, 14 days after bleaching, and 21 days after bleaching. The study found that there were significant differences be­tween the time intervals (P < .05); shear bond strength values of resin-based composite to enamel and dentin were lower immediately after the bleaching treatment. The authors concluded that 35% hydrogen peroxide reduces the bond strength to enamel and dentin. Clinically, the re­sults of this study suggest that clinicians should allow 7 days to elapse after completion of in-office bleaching with 35% hydrogen peroxide before plac­ing adhesive restorations.

 (Source: Jour­nal of the Amer­ican Dental Association, 2010, Volume 141, Number 3.)