The application of hydrogen peroxide in composite repair.

This study examined the influence of different surface conditioning methods on composite-to-composite microtensile bond strength. Thirty two-year old composite resin discs were randomly divided into three groups according to the different mechanical/chemical surface pretreatment tested: (1) 38% hydrogen peroxide (H(2)O(2))-treatment; (2) 50-microm aluminum oxide sandblasting; (3) no treatment. Depending on the intermediate agent applied, two subgroups were created: (A) three-step adhesive system; (B) prehydrolyzed silane coupling agent + three-step adhesive system. Microtensile bond strength measurements were performed and the data were statistically analyzed with Kruskall-Wallis Analysis of Variance and Dunn's multiple range test for post hoc comparisons (p < 0.05). Failure mode was evaluated with a scanning electron microscope. Changes in composite surface topography after H(2)O(2) treatment were also investigated. Composite repair strength did not benefit from H(2)O(2) treatment and adhesive application. Preliminary sandblasting significantly improved interfacial bond strength regardless of the intermediate agent applied. No changes in surface texture were produced after H(2)O(2) treatment. An atypical fracture pattern was detected at the interfacial level between H(2)O(2)-treated composite surfaces and the overlying adhesive and composite. H(2)O(2) treatment affected the composite-to-composite repair strength: a compromised resin polymerization may occur, resulting in a poor interfacial quality and a weak bond. Sandblasting still remains a reliable technique for composite repair.