Probiotics are living microorganisms that when administered in adequate amounts confer benefits to the health of the host. Probiotics are well studied in the medical field, the research on the use of probiotics for treatment of diseases in the oral cavity are successful, in which some dental specialties already use it in in vivo experiments, evidencing inhibition of inflammatory bone loss and alteration in immune modulation systemic. However, few studies have reported the effect of probiotic use on pulp infections. Therefore, the purpose of this study will be to evaluate the probiotics when consumed in the water as to their effect on the periapical lesion. The animals will be divided into four groups, as follows: Group I (4 animals / 8 teeth): Water without probiotic, without periapical lesion (3 days); Group II (4 animals / 8 teeth): Water with probiotic; without periapical lesion (3 days); Group III (12 animals / 24 teeth): Water without probiotic; with periapical lesion (7, 21, 42 days); Group IV (24 animals / 48 teeth): Water with probiotic; with periapical lesion (7, 21, 42 days). The animals will receive the probiotic administered orally (water consumed by the animals), Bifidobacterium animalis subsp. Lactis (B. lacti) HNO9 will be added to potable water having a volume of 10 milliliters, in the proportion of 1.5 x 10 to the power of 8th colony-forming units (CFU) per milliliters. The samples stained in Hematoxylin and eosin stain (HE) in optical microscopy will be analyzed by the description of the characteristics of the pulp tissue and of the apical and periapical regions, parallel to the morphometric analysis of the extension of the area of the periapical lesions, under fluorescent microscopy. It will be also evaluated osteoclast labeling and histoenzymology for tartrate-resistant acid phosphatase (TRAP) and immunohistochemical activity for identification of osteoclastogenesis markers (RANK, RANKL, OPG), furthermore, the microbiological analysis by the Brown & Brenn technique will be done. All analyzes and graphical representations will be performed with the help of GraphPad Prism 7 software (GraphPad Software Inc, San Diego CA, USA). The statistical tests applied will be selected according to the nature of the data. For all analyzes, the significance level of 5% will be considered.
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