## 4 Discussion  
In the presence of root canal infections, bacteria can penetrate dentin permeability at a depth of approximately 300 \(\upmu\)m, reducing the effectiveness of obturation techniques [27]. Therefore, this study evaluated the sealer penetration of three obturation methods evaluating the improvement achieved by sonicated techniques compared to conventional warm gutta-percha obturation techniques. The study was carried out using CLSM analysis, an investigation technique with several benefits compared to other imaging techniques [7; 11]. \begin{table}
\begin{tabular}{c c c c c c} \hline  & & **SB** & **T** & **ST** & \(p\)**-Value** \\ \hline \multirow{4}{*}{3 mm} & Depth (\(\upmu\)m) & 214.07 \(\pm\) 152.40 & 346.38 \(\pm\) 137.47 & 348.39 \(\pm\) 120.13 & \(p\) < 0.05 \({}^{\text{a}}\) \\  & Maximum depth (\(\upmu\)m) & 545.91 \(\pm\) 242.58 & 594.19 \(\pm\) 188.50 & 773.17 \(\pm\) 291.98 & NS \\  & Percentage (\%) & 51 \(\pm\) 18 & 59 \(\pm\) 11 & 54 \(\pm\) 14 & NS \\  & Area (\(\upmu\)m\({}^{2}\)) & 5396.05 \(\pm\) 4384.00 & 6962.35 \(\pm\) 5045.51 & 9092.69 \(\pm\) 3278.76 & NS \\ \hline \multirow{4}{*}{6 mm} & Depth (\(\upmu\)m) & 263.57 \(\pm\) 175.41 & 470.30 \(\pm\) 291.48 & 640.22 \(\pm\) 163.34 & \(p\) < 0.05 \({}^{\text{b}}\) \\  & Maximum depth (\(\upmu\)m) & 564.46 \(\pm\) 388.44 & 708.24 \(\pm\) 420.28 & 1156.79 \(\pm\) 117.87 & \(p\) < 0.05 \({}^{\text{c}}\) \\ \cline{1-1}  & Percentage (\%) & 53 \(\pm\) 19 & 59 \(\pm\) 13 & 65 \(\pm\) 13 & NS \\ \cline{1-1}  & Area (\(\upmu\)m\({}^{2}\)) & 7696.03 \(\pm\) 7585.38 & 8092.89 \(\pm\) 6114.97 & 15,997.06 \(\pm\) 8566.48 & \(p\) < 0.05 \({}^{\text{d}}\) \\ \hline \end{tabular} Data are reported as mean \(\pm\) standard deviation. SB: System B, T: non-sonicated Thermafil, ST: Sonicated Thermal: Significance: (a) ST vs. SB (\(p\) = 0.029, 1 \(-\)\(\beta\) = 0.52), (b) ST vs. CWT (\(p\) = 0.0019, 1 \(-\)\(\beta\) = 0.99), (c) ST vs. T (\(p\) = 0.015, 1 \(-\)\(\beta\) = 0.85), ST vs. SB (\(p\) < 0.001, 1 \(-\)\(\beta\) = 0.99), (d) ST vs. T (\(p\) = 0.028, 1 \(-\)\(\beta\) = 0.59), ST vs. SB (\(p\) = 0.028, 1 \(-\)\(\beta\) = 0.56).  
\end{table} 
Table 1: Comparisons. Figure 2: Representative CLSM images at 3 mm level (**a**–**c**) and 6 mm level (**d**–**f**) for the three groups. From our findings, Thermafil with sonicated activation ensures a significant deeper sealer penetration than that observed using either Thermafil without sonic activation or System B, according to previous studies, which demonstrated how sonicated activation may increase the sealer penetration and enhance lateral canal obturation [2; 11]. The deeper sealer penetration observed with Sonicated Thermafil could be due to a thermo-hydrodynamic effect able to push the sealer into dentinal tubules more intensely to obtain a more effective and hermetic seal thanks to the higher frequency, and the decreased time of the activation method could reduce the sealer noise and prevent voids and gap formation [2]. Our findings are similar to those of [PERSON] et al., according to which the intratubular penetration was similar using sonic or non-sonic activation techniques [28]. Moreover, it seems that the sealer penetration does not depend on the smear layer removal, but it is due to the physicochemical properties of the sealer and the used obturation technique [26], although the current literature is not unanimous on the role of the obturation technique in the sealer penetration [29]. According to [PERSON] et al. (2012), the sealer penetration percentage is a more noteworthy measurement than the maximum penetration; penetration of the sealer into dentinal tubules along the root canal circumference entails a mechanical improvement of the interface and contributes to preventing reinfection [10]. However, in this study, the percentage of sealer penetration was similar among the three groups, both at 3 and 6 mm; therefore, the sonic activation seemed unable to improve this parameter significantly.