Photodynamic therapy (PDT) is based on chemical, physical and biological processes that occur when a photosensitizer (PS) is activated by Laser or LED, to destroy the target cell. Strong evidence has proven the microbial reduction by PDT in Endodontics, potentializing the action of biomechanical preparation and intracanal medication. However, there are no studies about the effect of PDT on the bond strenght of fiber glass posts to intraradadicular dentin. The objective of the present study was to evaluate the effect of photodynamic therapy with methylene blue as a photosensitizer and calcium hydroxide intracanal, on the bond strength of glass-fiber posts (GFP) on the intraradicular dentin, and also to analyze the fracture pattern of the representative samples. It will be used 48 freshly extracted bovine incisor teeth, the biomechanical preparation (BP) in all root canals (RC) will be performed. To realize the PDT the methylene blue PS will be used, activated with Red Laser » 660nm. Distribution of the experimental groups: G1-BP + Deionized Water (Negative Control); G2-BP + Deionized Water + Ca(OH)2 (Positive Control); G3-BP + AM 0,005% + Ca(OH)2; G4-BP + AM 0,01% + Ca(OH)2; G5-BP + AM 0,005% + Red Laser (PDT) + Ca(OH)2; G6-BP + AM 0,01% + Red Laser (PDT) + Ca(OH)2. Proceeding, the RCs will then receive calcium hydroxide intracanal for 14 days. The removal of coronary seals and intracanal medication will be performed, and RCs will be filled and prepared for the cementation of the GFPs. The bond strenght of the glass-fiber posts (GFP) on the intraradicular dentin will be measured by the Push-Out test in a universal test machine with the slices obtained in the cervical, middle and apical thirds. The fracture pattern of the representative samples will be qualified by Scanning Electron Microscopy (SEM). The data obtained in the studies will be submitted to the normality test and the averages compared by specific statistical tests (± = 0.05).
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