## 3 Results  
Table 1 shows the variation in the canal area. The area increased in both groups without significant differences between them (\(p>0.05\)). For the SC group, the increase in the area after instrumentation with Rotate 25.06 was 33.63% (from 5.65 mm\({}^{2}\) to 7.55 mm\({}^{2}\)). After root canal obturation, this was 7.15% (from 7.55 mm\({}^{2}\) to 8.09 mm\({}^{2}\)). For the GF group, the increase in the area after instrumentation with Rotate 25.06 was 40.0% (from 5.2 mm\({}^{2}\) to 7.28 mm\({}^{2}\)). The increase after root canal obturation was 8.39% (from 7.28 mm\({}^{2}\) to 7.89 mm\({}^{2}\)). Table 2 shows the variation in the canal volume. The volume increased in both groups without significant differences between them. For the SC group, the increase in the volume after instrumentation with Rotate 25.06 was 44.38% (from 7.03 mm\({}^{3}\) to 10.15 mm\({}^{3}\)). The increase in the volume after root canal obturation was 77.07% (from 10.15 mm\({}^{3}\) to 17.98 mm\({}^{3}\)). \begin{table}
\begin{tabular}{l c c c c c c c c} \hline \hline \multirow{2}{*}{**Timing**} & \multicolumn{3}{c}{**Single Cone (\(n=11\))**} & \multicolumn{3}{c}{**Guttafusion (\(n=12\))**} & \multicolumn{3}{c}{**Difference**} \\ \cline{2-10}  & **Mean** & **SD** & **95\% CI** & **Mean** & **SD** & **95\% CI** & **Mean** & \(p\)**-Value** & **95\% CI** \\ \hline Before instrumentation & 5.65 & 0.99 & 4.98, 6.32 & 5.19 & 1.38 & 4.31, 6.07 & 0.46 & 0.370 & \(-\)0.59, 1.52 \\ After instrumentation & 7.55 & 1.05 & 6.85, 8.26 & 7.28 & 0.99 & 6.65, 7.91 & 0.27 & 0.531 & \(-\)0.61, 1.16 \\ After obturation & 8.09 & 0.78 & 7.57, 8.61 & 7.89 \({}^{*}\) & 1.05 & 7.14, 8.64 & 0.20 & 0.623 & \(-\)0.64, 1.04 \\ \hline \hline \end{tabular}  
* Available for 10 out of 12 elements. Abbreviations: SD, standard deviation; CI, confidence interval.  
\end{table} 
Table 1: Root canal area (mm\({}^{2}\)) measured on the X-rays, by timing and obturation technique. \begin{table}
\begin{tabular}{l c c c c c c c c c} \hline \hline \multirow{2}{*}{**Timing**} & \multicolumn{3}{c}{**Single Cone (\(n=11\))**} & \multicolumn{3}{c}{**Guttafusion (\(n=12\))**} & \multicolumn{3}{c}{**Difference**} \\ \cline{2-10}  & **Mean** & **SD** & **95\% CI** & **Mean** & **SD** & **95\% CI** & **Mean** & \(p\)**-Value** & **95\% CI** \\ \hline Before instrumentation & 7.03 & 2.65 & 5.25, 8.81 & 6.06 & 1.97 & 4.81, 7.32 & 0.97 & 0.331 & \(-\)1.05, 2.98 \\ After instrumentation & 10.15 & 2.55 & 8.44, 11.86 & 8.75 & 1.90 & 7.54, 9.95 & 1.41 & 0.146 & \(-\)0.53, 3.35 \\ After obturation & 17.98 & 4.61 & 14.88, 21.1 & 15.80 & 3.17 & 13.78, 17.8 & 2.18 & 0.196 & \(-\)1.22, 5.59 \\ \hline \hline \end{tabular}  
* Abbreviations: CBCT, cone beam computed tomography; SD, standard deviation; CI, confidence interval.  
\end{table} 
Table 2: Root canal volume (mm\({}^{3}\)) obtained through digital reconstruction of CBCT images, by timing and obturation technique. For the GF group, the increase in the volume after instrumentation with Rotate 25.06 was 44.4% (from 6.06 mm\({}^{3}\) to 8.75 mm\({}^{3}\)). The increase in the volume after root canal obturation was 80.57% (from 8.75 mm\({}^{3}\) to 15.80 mm\({}^{3}\)). Table 3 reports the remnant area after retreatment with RB40 and RB50 was measured for both groups. For the SC group, the remnants were 0.47 \(\pm\) 0.9 mm\({}^{2}\) after RB40 and 0.39 \(\pm\) 0.8 mm\({}^{2}\) after RB50, representing a reduction of 14.89%. For the GF group, the remnant area was 0.59 \(\pm\) 0.77 mm\({}^{2}\) after RB40 and 0.18 \(\pm\) 0.33 mm\({}^{2}\) after RB50, representing a reduction of 69.49%. Table 4 reports the remnant volume after the retreatment with RB40 and RB50 was evaluated. For the SC group, the remnant volume was 0.63 \(\pm\) 1.22 mm\({}^{3}\) after RB40 and 0.51 \(\pm\) 1.16 mm\({}^{3}\) after RB50, representing a reduction of 20.63%. For the GF group, the remnant volume was 0.55 \(\pm\) 0.91 mm\({}^{3}\) after RB40 and 0.36 \(\pm\) 0.59 mm\({}^{3}\) after RB50, representing a reduction of 36.36%.