## 4 Discussion
\begin{table}
\begin{tabular}{l c c c c c} \hline \hline  & **Apical** & \multicolumn{2}{c}{**Middle**} & \multicolumn{2}{c}{**Coronal**} \\ \hline
**Groups** & **Test Statistic** & \(p\) **Value** & **Test Statistic** & \(p\) **Value** & **Test Statistic** & \(p\) **Value** \\ \hline Automated irrigation vs. & & & & & \\ Passive ultrasonic irrigation & 7.071 & 0.03 \({}^{\star}\) & 7.000 & 0.03 \({}^{\star}\) & 4.857 & 0.01 \({}^{\star}\) \\ \hline Passive ultrasonic irrigation vs. & & & & & \\ Manual irrigation & 13.929 & 0.00 \({}^{\star}\) & 14.000 & 0.00 \({}^{\star}\) & 12.929 & 0.00 \({}^{\star}\) \\ \hline Automated irrigation vs. & & & & & \\ Manual irrigation & 6.857 & 0.03 \({}^{\star}\) & 7.000 & 0.03 \({}^{\star}\) & 8.071 & 0.01 \({}^{\star}\) \\ \hline \hline \end{tabular} \({}^{\star}\) The mean difference is significant at the 0.05 level.  
\end{table} 
Table 3: Pairwise comparison of mean smear scores. levels, which were around 3.48 \(\pm\) 0.36, 2.64 \(\pm\) 0.32, and 1.22 \(\pm\) 0.24 in the manual irrigation, automated irrigation, and passive ultrasonic irrigation groups, respectively, compared with the debris score recorded in the other two-thirds of the teeth. The recorded smear scores were higher at the apical level as well, and it was around 3.02 \(\pm\) 0.25, 2.70 \(\pm\) 0.21, 1.15 \(\pm\) 0.19 in the manual irrigation, automated irrigation, and passive ultrasonic irrigation groups, respectively. SEM analysis of different groups showed the least smear and debris scores with the passive ultrasonic irrigation group. Higher debris and smear layer scores were observed in the manual irrigation group. Among the various sections assessed, the coronal section elicited the least debris and smear scores, whereas the apical section showed a higher accumulation of smear layer and debris. Evaluating individually the technique compared in this study, the score differences obtained in the three-thirds using the PUI technique are low and not statistically significant (\(p\) > 0.05) (Table 1) (Figure 3). This result might suggest that as the technique allows the clinician to clean the coronal third of the root canal system, it guarantees the cleaning of the other two-third, with only few small debris particles and dental tubules opened. In contrast, the manual irrigation technique determines a homogeneous smear layer covering the root canal wall and only few dental tubules open, along all the three-thirds of the endodontic canal (\(p\) > 0.05) (Table 1) (Figure 3). The automated irrigation (AI), as in the PUI technique, is able to remove debris and smear layers at the coronal and middle third, with several dentin tubules opened (1.42 \(\pm\) 0.13 and 1.87 \(\pm\) 0.14, respectively) (Table 1) (Figure 3); however, differently from the PUI, it has a statistically significantly worse ability (\(p\) < 0.05) in cleaning the apical third, managing to obtain only a few open dental canals (2.70 \(\pm\) 0.21) (Table 1) (Figure 3). Studies claim the inefficiency in thoroughly achieving the disinfection at the apical one-third [14; 25; 26]. When collectively considered, the literature states the inefficiency of the SNI in achieving effective disinfection and debridement [27], smear and debris removal [28], and irrigant replacement [29]. Hence, activation is claimed to be important in achieving better and more effective cleansing of the root canal system [30]. Effective root canal irrigation always depends on the choice of root canal irrigant used along with the mode of usage [31]. Although the chemical properties of the irrigating solution are claimed to be important in enhancing the primary role of the root canal irrigant, various other factors, such as the volume of irrigant used, contact time, temperature, and mode of delivery play a wider role in enhancing the irrigant activity [32].