The absence of studies addressing the ability of Er: YAG laser associated to sodium fluoride at 0.05% in controlling the demineralization of tooth enamel, this study aims to evaluate the effect of the combination of laser irradiation Er:YAG to sodium fluoride at 0.05% in the inhibition of progression of carious lesions in enamel. 80 pieces of bovine incisors (3x3mm) will be included in polyester resin, ground flat and polished. Readings will be held microhardness (KNH) subsurface (baseline) to standardize the samples, and then 60 samples are selected based on the average of the results of microhardness. Initial carious lesions will be developed in the specimens during five days of cycling demineralizing and remineralizing solution. After the initial injury, the specimens will be randomly divided into four groups (n = 15): Irradiation with Er:YAG + sodium fluoride to 0.05%, irradiation with Er:YAG laser + placebo (control) ; sodium fluoride to 0.05% placebo (control). The laser Er: YAG will be spent in non-contact, out of focus, with energy density of 3.7 J/cm2, with distance from the tip / substrate of about 4 mm. The fragments will be immersed in 15ml of sodium fluoride to 0.05% or placebo for 1 minute per day for 14 consecutive days. After completion of treatments, will be held to pH cycling for 14 days, and then the specimens will be submitted to the evaluation of the microhardness 30µm from the surface. The data will be analyzed to choose the appropriate statistical method.
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