This study will evaluate by laboratory test the penetration of hydrogen peroxide on dental tissues and by clinical analysis the sensibility and color alteration of dental structure, after different application times (30 minutes, 1, 2, 4 and 8 hours daily) on enamel surface of a 10% carbamide peroxide bleaching gel. A total of 75 patients, aged 18-25 years, will participate of this clinical study and who have not yet undergone the dental bleaching. The response variables for the clinical analysis will be dental color alteration, that will be held in the superior and inferior incisors and canines teeth, by the visual method (Classical Vita, Vita Zahnfabrik, Germany) and digital (Easyshade Vita, Vita Zahnfabrik, Germany), at baseline, immediately after, at 24 hours, 6 and 12 monthsafter dental bleaching; and dental sensitivity, which will be analyzed by visual analog and measured prior, during, immediately after and 24 hours after dental bleaching. These variables will be analyzed and noted during the sessions. The microscopic analysis of enamel surface will be examined by scanning electron microscopy (SEM), through replicas obtained clinically of the superior central incisors before, immediately after, 6 and 12 months after bleaching procedures. For laboratory test will be used blocks of bovine enamel and dentin. The study variable, for laboratory analysis, will be to quantify the penetration trans/enamel/dentin of hydrogen peroxide at different times of application of carbamide peroxide 10% in the enamel surface enamel (30 minutes, 1, 2, 4 and 8 hour). Considering the qualitative ordinal response variable, will be applied appropriate statistical tests to analyze the results, at a significance level of 5%.
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