The objective of this study will be to evaluate the effects of calcium and fluorideions of addition to the formulation of a 35% hydrogen peroxide bleaching gel in its penetration through the tooth structure, whitening efficacy and micro hardness of dental enamel. It will be used 80 bovine incisors, from which will be obtained enamel/dentin discs from the buccal surface, with 6 mm diameter and 2mm thick (1mm of enamel and1mm of dentin). The samples will be divided into four groups depending on the protective/remineralizing substances added to the hydrogen peroxide gel 35%: GroupCa - 0.5% of Calcium Gluconate; Group F - 0.2% of Sodium Fluoride; Group Ca+F -0.5% Calcium Gluconate and 0.2% Sodium Fluoride; Control Group - no additional agent will be added. The baseline color and enamel microhardness of the samples will be measured before bleaching procedures. The specimens of each group will be placed in a metal holder in which there will be an internal cavity to simulate the pulpchamber, which will be filled with acetate buffer to collect peroxide. The whitening gels will be applied for 30 min, divided into 3 applications. The amount of peroxide which passed through the samples will be determined by absorbance spectrophotometry. Themicrohardness will be measured again immediately after bleaching. The samples will be immersed in artificial saliva for 7 days, after that the color will be reassessed. The data will be statistically analyzed, adopting a significance level of 5%.
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