Clinical studies evaluating chlorhexidine, used for rehydration of dentin, in order to preserve the hybrid layer in cavities prepared with Er: YAG are needed as available in the literature. The aim of this study is evaluate clinically composite restorations, in preparation with Er: YAG laser or bur, rehydrated with water or chlorhexidine over time, by analyzing clinical, photographic and scanning electron microscopy (SEM). Thirty individuals who have at least four active caries with cavitation reaching the dentin located on the occlusal surface of molars counterparts are selected. The teeth of each individual will be randomly assigned into two groups: (I) Er: YAG laser (260 mJ / 4 Hz) re-wetting with chlorhexidine, (II) Er: YAG laser (260 mJ / 4 Hz) re-wetting with deionized water (III) Conventional method (high-speed turbine and low speed handpiece) re-wetting with chlorhexidine and (IV) Conventional method (high-speed turbine and low speed handpiece) re-wetting with deionized water. The teeth will be isolated, prepared cavities, phosphoric acid-etching, re-wetting according the method of re-wetting and restored employing the Single Bond 2 (3M) and Z350XT resin (3M). Clinical follow-up will be held after the polishing of the restoration (Baseline), 6 and 12 months of the making of the restoration using the modified USPHS criteria. The restorations will be qualitatively analyzed by means of photographs. In the evaluation period, the teeth are shaped and made of epoxy resin replicas that will be quantitatively analyzed by SEM with increases of 20X to 200X, which will measure the distance between the cavosurface angle and the margin restoration (gap) using software (AxioVision 3.1). Data will be analyzed by statistical method is appropriate.
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