Effect of Hydrogen Peroxide 38% in the Occurence of Microleakage

Objectives: the purpose of this work was to evaluate the occurance of microleakage in composite resin restorations made after bleaching using peroxide hydrogen 38%. Methods: for that, 20 pre molars were randomly distributed in 4 study groups, being submitted to the action of the product Opalescence Xtra Boost (Ultadent Products) according to the specifications of the manufacturer, so Group I: considered control, the restorations were made on teeth that were not bleached; Group II: the restorations were made immediately after bleaching; Group III: the restorations were made 7 days after bleaching; Group IV: the restorations were made 21 days after bleaching. Passed the time interval, Class V cavities were made with oclusal margins in beveled enamel and cervical in dentin/cementum, being restored with an one-bottle adhesive system and composite resin. Next, the specimes received 1000 thermal cycles (5+/-1oC to 55+/-1oC) and were immersed in coloring solution (methilene blue). After that, they were sectioned and evaluated by stereomicroscopy. Scores were attributed to avaluate the dye penetration in enamel and dentin/cementum margins, being the data submitted to the Kruskal Wallis statistical test at level 5%. Results: for both margins (enamel and dentin/cementum) the using of the bleaching product did not caused a significative increasing of the microleakage. Conclusions: the results demonstrated that the interval time for the restorations to be made was not significative in the occurance of microleakage in anyone of the margins avaluated of tooth previously bleached with peroxide hydrogen 38%.