There are not many studies consistently investigating the ability of different approaches to disinfect oval-shaped canals. In a recent study, Siqueira et al (14) compared the in vitro capability of a newly developed instrument, the self-adjusting file, and rotary NiTi instrumentation to eliminate Enterococcus faecalis populations from long oval root canals. They observed that rotary NiTi instrumentation used with Ferroptosis mutation syringe/needle irrigation failed to predictably disinfect root canals and was significantly less effective than the

self-adjusting file. The difficulty of effectively cleaning and disinfecting oval-shaped canals open perspectives to the use of alternative or supplementary approaches. Postinstrumentation supplementary approaches have been proposed to improve and/or expedite root canal disinfection. For instance, to take advantage of the benefits of both NaOCl and chlorhexidine (CHX) as irrigants, it has been recommended to use NaOCl

during preparation and to supplement disinfection by a final rinse with CHX 15 and 16. Activation of the irrigant solution has also been recommended, and among the methods available, passive ultrasonic irrigation (PUI) is probably the most used (17). PUI refers to either intracanal placement of an irrigant with a syringe followed by ultrasonic activation or continuous delivery of irrigant through an ultrasonic handpiece (18). PUI has been shown to be more effective than other irrigation systems in removing tissue remnants and dentinal debris from KU-55933 in vitro the main root canal as well as from irregularities Urease 19, 20, 21 and 22. Based on these reports, it seems interesting to test the effects of PUI and the CHX final rinse on oval-shaped root canal disinfection. The present study was undertaken to investigate the ability of different approaches to supplement the intracanal antibacterial effects of rotary NiTi instrumentation against E.

faecalis populations in long oval root canals of extracted human teeth. This study used 54 extracted teeth (single-rooted and single-canaled mandibular incisors and maxillary second premolars) with long oval root canals obtained from an existing collection of extracted teeth at Estácio de Sá University. These teeth were extracted for reasons not related to this study, and approval for the study protocol was obtained from the Ethics Committee of the Estácio de Sá University. Teeth were selected on the basis of radiographs taken in both buccolingual and mesiodistal directions. Selected teeth had root canals presenting a greater than 2.5:1 ratio between the buccolingual and mesiodistal dimensions at a level 5 mm from the root apex. Pairs of teeth were selected on the basis of similar radiographic root canal morphology, and each tooth from each pair was randomly assigned to each experimental group.