Influence of Bleaching in Occurance of Microleakage

Objectives: the purpose of this work was to avaluate the occurrence of microleakage in resin compose restorations made after tooth bleaching with carbamide peroxide 15% during 3 weeks with 4 hours of daily applications. Methods: for that, the tooth were distributed in 4 study groups: Group I: considered control, the restorations were made on teeth that were not submitted on the product's action; Group II: the restorations were made immediately after bleaching, Group III: the restorations were made 7 days after bleaching, Group IV: the restorations were substituted 21 days after bleaching. After the bleaching treatment Class V restorations were made presenting oclusal margins in beveled enamel and cervical in dentin/cementum. The 40 cavities were 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 methilene blue solution for 4 hours. After that, they were sectioned and evaluated by stereomicroscopy and scores were attributed for the occurance of the stain's penetration in the interface teeth/restoration. The obtained data were subjecte to the Kruskal Wallis statistical test at level 5%. Results: the use of the product caused a signifcative increasing of microleakage in enamel margins when the restorations were made immediately after bleaching. When the dentin/cementum margins were analysed, it was noted that the interval time did not influenced the occurance of microleakage. Conclusions: the results indicated that, in relation to the enamel, is necessary to wait at least 7 days after bleaching to make resin composed restorations. However, for margis located in dentin the time interval for the restorations to be made was not significative.