## 4 Discussion
When the efficacy of root canal irrigation has to be considered, it should effectively remove the organic and inorganic tissue debris from the root canal walls [33], have better microbial and biofilm removal [34] and better removal of the loosely and tightly adhered smear and debris from the root canal surface, and leave canals cleaner and better for effective bonding during the obturation [35]. An enormous body of literature with substantial evidence is available on ultrasonic activation techniques [36; 37]. Compared with manual irrigation, the ultrasonic activation promotes the acoustic flow within the root canal system. The forces caused on the root canal walls causes enormous shear wall stress, leading to the dislodgement of bacterial smear from the root canal system. This phenomenon is clearly lacking in the conventional needle-based irrigation. A recent systematic review has highlighted the importance of using an activation device for better root canal cleanliness [28]. However, there was no justification provided on the specific activation device for better smear and debris removal. [PERSON] et al. [38] assessed the effect of master apical file size and taper on root canal cleanliness in single-rooted specimens. According to their study results, the specimens which have been enlarged to 0.06 taper and a 30 size minimum seemed to achieve an acceptable root canal debridement [38]. The current data also suggest better smear and debris removal when the specimens were shaped to a size greater than 25 [39]. The irrigation protocol, volume, and concentration were constant in all the groups. To date, there is only one study which assessed in vitro smear removal of an automated root canal irrigation device [16] and evidence is also scarce in the literature on the efficacy of this novel irrigation device, which still needs to be explored in future study designs. Current evidence is always in favor of the use of the activation devices with no justification of the superiority of one device over the others [28]. Overall, analyzing in vitro studies on passive ultrasonic activation, the data showed favorable results on pulp tissue removal [37], hard tissue debris removal [40], better root canal disinfection [36], and overall improvement in root canal debridement [32] on using ultrasonic activation as compared to the other experimental modes used. Current study results also showed better debris and smear removal by using an ultrasonic activation device. Although it is mandatory to apply activation after the complete root canal instrumentation, the usage of activation devices during the preparatory phases causes extensive extrusion of debris produced in the root canal system [41]. Hence, the currently developed automated irrigation device could benefit by delivering the irrigant at a constant flow rate, preventing the irrigant extrusion and reducing operator fatigue. The limitations of the current study were only considering the constant flow rates. Single-rooted teeth with minimal curvatures with adequate shaping were considered in the present study. So, the real-time benefit of the device could not be explored to its full potential as better smear removal could also have been attributed partly to instrumentation. Therefore, future studies can assess irrigant flow rates and their canal cleaning ability in minimal shapes with acute curvature and assess their efficiency.