Discussion
tooth
ENLARGEMENT
The fundamental goal of root canal therapy is disinfection of the root canal system followed by proper coronal and apical sealing, while the role of shaping is to remove infected dentin and provide space for irrigant penetration and subsequent obturation. Irrigation during shaping does not eliminate half of the debris that accumulates throughout instrumentation especially in the apical third [The copper cube allowed the investigation of root cross sections at the different stages of root canal preparation and irrigation so that each tooth served as its own control for a true analysis of the change in anastomosis cleanliness [The major objective of this study was comparing the cleaning efficacy of different irrigation activation techniques per se. Therefore, a simple irrigation protocol with only NaOCl was chosen to eliminate the added effect of any chelating agents as justified in several previous studies [Roots were decoronated to standardize root length. This can be regarded as a technical limitation in this study because this allows easier access to the root canals, and there is no coronal reservoir of irrigation solution. Previous studies that focused on the prevalence of root canal isthmuses through different methodologies revealed high prevalence in mesiobuccal roots of maxillary molars and mesial roots of mandibular molars [Samples were analyzed under a stereomicroscope at 30 × magnification because it allowed clear visualization of both root canals and anastomoses in the same frame, in contrast to other studies that employed scanning electron microscope in which only limited areas of the section could be scanned [All the final irrigation techniques used in this study resulted in significant improvement in anastomosis cleanliness. As increasing the irrigant volume and activating it results in improved cleanliness [The least improvement in anastomosis cleanliness occurred in the control group (NA) (Figs. At the 4 mm and 6 mm levels, the difference between EDDY and PUI was insignificant. This can be attributed to the larger canal diameter at these levels, which allowed less-restricted vibration of both tips. This came in harmony with the previously published data comparing sonic to ultrasonic activation [Regarding the intragroup analysis of NA, the 2 mm level showed the highest CD. This can be explained by the fact that after cleaning and shaping, this area is the one with the most packed residual debris [PUI at the 2 mm level was less effective than 4 mm but similar to 6 mm without significant difference. This can be attributed to the narrowness of this area may results in a more file-to-wall contact than the middle. Some of the samples even showed signs of canal deformation due to the ultrasonic tip touching the walls while vibrating (Fig. It is important to emphasize that in this study, 1 mL of irrigant was activated for 30 s to investigate the exclusive effect of the activation technique. Increasing the irrigant volume, activation time, using a chelating agent and increasing the final apical enlargement size are considered limitations of the present study which may have different implications on the overall anastomosis cleanliness [