The cleaning of tissue debris and elimination of root canal infection provide a favorable environment for repair of periapical lesions, and favor the adequate root canal obturation. Therefore the aim of this study is to analyze the quality of endodontic fillings in mesial canals of mandibular molars in function of apical dilation, dilating instrument to the initial diameter of 0.25 mm or diameter 0.40 mm and the employment of ultrason and sodium hypochlorite solution 1% in the final irrigation. It will be selected 56 mesial roots of human molars with roots intact with a maximum curvature of 30 ° (Schneider), complete apex obtained through donations made by professional of molar extracted and consented to its use in research by the patient. Previously, pilot tests will be conducted using 8 roots, with two teeth per group for training of rotary instrumentation and techniques shutters. The other 48 roots will be employed in the research. Initial radiographs will be to verify the presence of two mesial canals with separate forame. The teeth will be divided into 4 groups of 12 teeth according to the level of expansion and employment of ultrason with sodium hypochlorite 1% in the final irrigation, obeying the following: G1: # 25 without ultrasound; G2: # 40 without ultrasound; G3: # 25 with ultrasound; G4: # 40 with ultrasound. After preparation of the canals and final irrigation, the teeth will be filled by technical System B and AH Plus sealer with 0.1% rhodamine. After filling teeth, they will be held 72 hours at 37 ° C and 100% humidity. After this period the teeth will be sectioned at 2, 4 and 6 mm. The sections will be analyzed in esteriomicroscopy and confocal microscopy. The sections will be analyzed for the presence of voids, sealer and gutta-percha areas. The date will be compared statistically.
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