Negative pressure irrigation (ENDOVAC) versus conventional irrigation: histopathology, immunohistochemistry and histoenzimology study, in dogs' teeth with apical periodontitis

Abstract

Root canal system irrigation is an extremely important step of endodontic therapy. Traditional irrigation is not able to deliver the irrigating solution 1 mm beyond the needle tip, being relatively ineffective in cleaning the apical third of the root canal walls. An alternative method for root canal system irrigation using negative apical pressure has recently been introduced (EndoVac; Discus Dental, Culver City, CA, USA). According to the literature, it has greater cleaning potential, safety and capacity of eliminating the microbial content of the root canal system, with less extrusion of irrigating solution to the periapical tissues. Therefore, the aim of this study will be to evaluate in vivo by histopathological analysis, immunohistochemistry and histoenzymology, the repair of apical and periapical tissues after use of apical negative pressure irrigation (EndoVac) compared with conventional irrigation in immature dog's teeth with and apical periodontitis. Forty immature teeth (80 root canals) from 4 Beagle dogs will be selected for this study and divided into 4 groups: I (irrigation with EndoVac system), II (conventional irrigation), III (teeth with apical periodontitis and no endodontic treatment) and IV (sound teeth without endodontic treatment). After an experimental period of 90 days, the animals will be euthanized and the histotechnical processing will be carried out. Five-micrometer-thick sections will be obtained, stained with hematoxylin and eosin (HE) and examined with an appropriate microscope. In all groups, the morphometric analysis of the extension of the periapical lesions and area of mineralized tissue deposited in the apical region will be performed by fluorescence microscopy in the HE-stained sections. In addition, Brown and Brenn staining will be performed to evaluate the presence of bacteria and their localization, tartrate-resistant acid phosphatase (TRAP) histoenzymology will be performed for identification of osteoclasts, and alizarin red staining will be performed for identification of calcium deposits in areas of mineralized matrix. Immunostaining for osteopontin and phosphatase alkaline will also be performed, which are markers for osteoblast differentiation and for the osteoblast-specific transcription factor Runx2, which is essential for osteoblast differentiation. The results will be expressed qualitatively, considering the presence/absence and localization of immunostaining reactions. All analyses will be undertaken by an experienced and calibrated examiner blinded to the groups under evaluation. The obtained data will be subjected to appropriate statistical analysis with significance level of 5%. (AU)