## 3 Results
### Assessment of Intracanal Remnants: X-rays and CBCT  
The pre-operative root canal area was calculated using X-rays. No differences were observed between the two groups (\(p>0.05\)). The root canal areas were then calculated on the X-rays, respectively, after the completion of the first endodontic treatment, after the completion of the SRCTs procedures with the RB #25, and after the use of the RB #40 as reported in Table 2.  
SRCTs with RB #25 increased root canal area by 12% for SC group and 14% for GF group compared to the pre-operative root canal area. The use of RB #40 further increased the area of root canal by 8% in both groups compared to the previous treatment with RB #25. Table 3 reports the mean values of the remnants areas (mm\({}^{2}\)) and volumes (mm\({}^{3}\)) at the coronal, middle, and apical thirds. In both filling groups, the remnants occupied a large portion of the middle third of the canals. The coronal and apical thirds showed lower levels of remnants. The area of the remnants in the middle thirds was statistically significantly higher than that measured in the coronal and apical thirds. \begin{table}
\begin{tabular}{c c c} \hline
**Group** & **SRCT \#25 Time** & **SRCT \#40 Time** \\ \hline SC Group (n = 32) & 7.02 \(\pm\) 1.10 & 1.18 \(\pm\) 0.53 \\ \hline GF Group (n = 32) & 8.22 \(\pm\) 1.20 & 2.00 \(\pm\) 1.10 \\ \hline \end{tabular}
\end{table} 
Table 1: Working time (min) calculated to perform the secondary treatment with RB #25 and completed with RB #40. Mean \(\pm\) Standard Deviations. \begin{table}
\begin{tabular}{c c c c} \hline
**Group** & **Preoperative** & **Post-Treatment** & **SRCT \#25** & **SRCT \#40** \\ \hline AHPlus/SingleCone (n = 32) & 4.87 \(\pm\) 0.65 & 7.11 \(\pm\) 0.78 (+46\%) & 7.94 \(\pm\) 0.63 (+12\%) & 8.53 \(\pm\) 0.65 (+8\%) \\ \hline AHPlus/KuttaFusion (n = 32) & 4.82 \(\pm\) 0.61 & 6.97 \(\pm\) 0.81 (+45\%) & 7.98 \(\pm\) 0.60 (+14\%) & 8.61 \(\pm\) 0.61 (+8\%) \\ \hline \end{tabular}
\end{table} 
Table 2: Root canal Area (mm\({}^{2}\)) calculated on radiography: preoperative, post-treatment, after secondary treatments with RB #25 and with RB #40. Percentage of increase after each treatment is reported. Mean \(\pm\) Standard Deviations. Tables 4 and 5 report the correlation of the remnants areas measured by X-ray and the remnants volumes measured by CBCT. Both radiological examinations were able to detect the same remnants in the canal third with the exception of the apical third of the GF group, in which discrepancies were found. \begin{table}
\begin{tabular}{c c c c c c} \hline  & & **Apical Third** & **Middle Third** & **Coronal Third** & **Total** \\  & & **Area** & **Area** & **Area** & **Area** \\ \hline \multirow{3}{*}{Apical Third} & Pearson correlation & 0.516 & 0.404 & 0.137 & 0.493 \\  & \(p\) value & 0.0001 & 0.002 & 0.172 & 0.0001 \\  & N & 32 & 32 & 32 & 32 \\ \hline \multirow{3}{*}{Middle Third} & Pearson correlation & 0.270 & 0.586 & 0.322 & 0.594 \\  & \(p\) value & 0.028 & 0.0001 & 0.014 & 0.0001 \\  & N & 32 & 32 & 32 & 32 \\ \hline \multirow{3}{*}{Coronal Third} & Pearson correlation & \(-\)0.087 & 0.133 & 0.651 & 0.262 \\  & \(p\) value & 0.277 & 0.182 & 0.0001 & 0.034 \\  & N & 32 & 32 & 32 & 32 \\ \hline \multirow{3}{*}{Total Volume} & Pearson correlation & 0.290 & 0.575 & 0.473 & 0.678 \\  & \(p\) value & 0.018 & 0.0001 & 0.0001 & 0.0001 \\ \cline{1-1}  & N & 32 & 32 & 32 & 32 \\ \hline \end{tabular}
\end{table} 
Table 4: Pearson correlation of areas and volumes of SC group (\(p\) value was set at 0.05). \begin{table}