## 3 Results  
There was no statistically significant difference between the groups in terms of volume change after root canal preparation in the mesio-buccal and mesio-lingual canals (\(p>0.05\)). The use of OR or PU did not affect volume change (\(p>0.05\)). Table 1 shows the values for volume change, surface area change, non-instrumented area change and danger zone change after canal preparation of the mesio-buccal and mesio-lingual canals. There was no statistical difference between the groups in terms of changes in the surface area of the mesio-buccal and mesio-lingual canals after root canal preparation (\(p>0.05\)). The use of OR or PU did not affect the change in surface area (\(p>0.05\)). Table 1 shows the values for volume change, surface area change, non-instrumented area change and danger zone change after canal preparation of the mesio-buccal and mesio-lingual canals. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Parameters**} & \multicolumn{5}{c}{**Groups**} \\ \cline{2-7}  & **TAC-OR (\(n=15\))** & **CAC-OR (\(n=15\))** & **\(p\) Values** & **TAC-PU (\(n=15\))** & **CAC-PU (\(n=15\))** & **\(p\)-Values** \\ \hline \multirow{2}{*}{\(\Delta\) Volume Change (mm\({}^{3}\))} & MB 4.16 \(\pm\) 0.28 & MB 4.48 \(\pm\) 0.27 & \(p=0.38\) & MB 4.06 \(\pm\) 0.44 & MB 4.28 \(\pm\) 0.66 & \(p=0.74\) \\ \cline{2-7}  & ML 4.41 \(\pm\) 0.52 & ML 4.33 \(\pm\) 0.33 & \(p=0.87\) & ML 4.87 \(\pm\) 0.48 & ML 4.04 \(\pm\) 0.42 & \(p=0.06\) \\ \hline \multirow{2}{*}{\(\Delta\) Surface Area (mm\({}^{2}\))} & MB 6.93 \(\pm\) 0.31 & MB 6.40 \(\pm\) 0.4 & \(p=0.21\) & MB 7.03 \(\pm\) 0.25 & MB 6.80 \(\pm\) 0.41 & \(p=0.37\) \\ \cline{2-7}  & ML 5.79 \(\pm\) 0.33 & ML 5.89 \(\pm\) 0.27 & \(p=0.75\) & ML 6.01 \(\pm\) 0.31 & ML 5.83 \(\pm\) 0.25 & \(p=0.59\) \\ \hline \multirow{2}{*}{Non-Instrumented Area (\%)} & MB 11.82 \(\pm\) 0.25 & MB 16.08 \(\pm\) 0.46 & \(p<0.001\) & MB 11.76 \(\pm\) 0.17 & MB 15.41 \(\pm\) 0.31 & \(p<0.001\) \\ \cline{2-7}  & ML 11.69 \(\pm\) 0.15 & ML 16.76 \(\pm\) 0.14 & \(p<0.001\) & ML 11.44 \(\pm\) 0.18 & ML 15.55 \(\pm\) 0.08 & \(p<0.001\) \\ \hline \multirow{2}{*}{\(\Delta\) Danger zone (mm)} & MB 0.30 \(\pm\) 0.05 & MB 0.29 \(\pm\) 0.05 & \(p=0.91\) & MB 0.25 \(\pm\) 0.07 & MB 0.23 \(\pm\) 0.06 & \(p=0.67\) \\ \cline{2-7}  & ML 0.26 \(\pm\) 0.04 & ML 0.24 \(\pm\) 0.08 & \(p=0.83\) & ML 0.28 \(\pm\) 0.05 & ML 0.22 \(\pm\) 0.04 & \(p=0.17\) \\ \hline \multirow{2}{*}{TAC-OR: traditional access cavity—One Reci, TAC-PU: traditional access cavity—ProTaper Ultimate, CAC-OR: conservative access cavity—One-Reci, CAC-PU: conservative access cavity—ProTaper Ultimate, MB: mesio-buccal, ML: meso-lingual.} & & & & \\ \end{tabular}
\end{table} 
Table 1: The mean \(\pm\) standard deviation values of volume change, surface area, non-instrumented area, and the thickness of dentin in the danger zone area. In Figure 5, the STL images obtained by micro-CT pre- and post-instrumentation were presented to all groups in the study, as well as the images obtained by superimposing these images. Regardless of the file system used, more canal transportation was observed in the CAC groups at a distance of 2 mm, 5 mm, and 8 mm from the apical region (\(p<0.05\)). The use of OR or PU did not affect canal transportation (\(p>0.05\)). In Table 2, the mean transportation values of the meso-buccal canals at a distance of 2 mm, 5 mm, and 8 mm from the apical region are given. Table 2 shows statistically significant differences between the CAC and TAC groups without the effect of the PU and OR subgroups in terms of transportation in all measured distances from the apical region in the mesoibuccal canals. In Table 3, the mean transportation values at distances of 2 mm, 5 mm, and 8 mm from the apical region of the meso-lingual canals are given. Table 3 shows statistically significant differences between the CAC and TAC groups without the effect of the PU and OR subgroups in terms of transportation in all measured distances from the apical region in the mesoibingual canals. Figure 5: _Cont._