The present study aims to evaluate the color alteration, trans-enameland trans-dentinal cytotoxicity and diffusion of hydrogen peroxide (HP) on bovine enamel / dentin specimens, which are divided into 9 groups. The specimens of groups 2-9 will be pigmented with hemolysate blood. Groups 1 (no pigmentation) and 2 will be control groups, without blwaching treatment. The Groups 3 and 4 will receive 10% carbamide peroxide (CP), for 90 or 180 minutes, respectively; the Groups 5 and 6 will receive 6% HP for 90 or 45 minutes,respectively, Group 7 will receive 20% HP, for 50 minutes. The groups 3-6 will receive treatment for 21 days. The groups 8 and 9 will receive 35% HP, in Group 8 the bleaching gel will beapplied and exchanged two times in every 15 minutes and group 9 bleachimg gel will be applied only once,both totaling 45 minutes. Groups 7, 8 and 9 will receive bleaching three sessions, one for week. To quantify the penetration of the peroxide, the specimens will be positioned in artificial pulp chamber (APB) containing acetate buffer solution, which will be collected for evaluation of optical density in a spectrophotometer. The analysis of the color change will be performed by reflection spectrophotometry. The readings will be performed 7 days after each in-office bleaching session or after each week of at- home bleaching and 7 days after the end of treatment. For cytotoxicity analysis, the specimens will be adapted in CPAs, and extracts (products of bleaching + diffusion culture medium) will be applied on odontoblast like cells MDPC- 23 culture for 1 hour. The viability and cell morphology will be evaluated by the MTT assay and SEM, respectively. Results will be subjected to appropriate statistical analysis.
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