Photodynamic therapy (PDT) is an aggregate of physical, chemical and biological procedures that occur after use of photosensitizer (PS) which is active by visible light, with a specific wavelength, to aim to destroy the target cells. Actually, strong evidences show the efficacy on microorganism reduction promotes by PDT, however there is no studies on literature show the influence of PDT on mechanical proprieties of the intraradicular dentin. The aim of the study will be to evaluate the influence of PDT on the bond strength of glass fiber posts in different thirds of intraradicular dentin (cervical, middle and apical), through the push-out test. For this study forty freshly extracted bovine incisors will be used. Previous x-ray will be performed to confirm the integrity of the tooth structure. The biomechanical preparation in all root canals with K file, which the final instrument a K #80, 1 mm short of root apex and irrigation with 1% sodium hypochlorite. The five group (n=8) will be distribute: G1-control (deionized water); G2-curcumin PS 500 mg/L; G3-curcumin PS 500 mg/L + blue Led (PDT); G4-curcumin PS 1000 mg/L; G5-curcumin PS 1000 mg/L + blue Led (PDT). Both groups (G2 to G5) will receive curcumin PS for 5 minutes (pre-irradiation period) mixed with ultrasound by 60 seconds passive irrigation (without refrigeration) on endodontic scale 2 and a K file #25 positioned 2mm before the working length. On G3 and G5, the curcumin PS will be activated with Led » 480 nm, 75 J/cm² fluency, by four minutes, helped by an optical fiber with a 500-¼m diameter length positioned 2mm before the working length. Then all root canals will be dried and filled, using a main #80 guta-percha cone and accessory cones F and MF. Root canal will be prepared for receive glass fiber posts White DCE #2 (FGM), once will be cemented into to the root canal with RelyX U200 (3M Espe) self-adhesive resin cement. The bond strength will be measured using the push-out test in a universal assay machine on the three parts of intracanal dentin (cervical, middle and apical). The data will be submitted to normality test and the means will be compared by specific statistical tests (±=0.05). Representative samples of each group will be analyzed with scanning electron microscopy.
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