## 3 Results  
Table 2 reports mean and standard deviation of change (\(\Delta\)) in maximum mesiodistal and buccolingual dimensions.  
In the MD direction, the cutting efficiency was not significantly different between 2 Shape and Hyflex CM in the apical and coronal thirds while it was significantly greater for 2 Shape in the middle third (\(p<0.05\)). Considering the total root canal space, the two systems were not significantly different (\(p>0.05\)). The cutting efficiency of 2 Shape was not significantly dissimilar between the anatomical thirds (\(p>0.05\)) while it was significantly higher in the coronal for Hyflex CM (\(p<0.05\)).  
In the BL direction, 2 Shape and Hyflex CM had no statistically significant differences in the all-anatomical thirds (\(p>0.05\)). Considering the total root canal space, 2 Shape had significantly higher cutting efficiency compared with Hyflex CM (\(p<0.05\)). The cutting efficiency of 2 Shape was not significantly different in all anatomical thirds (\(p>0.05\)). Likewise, no statistically significant difference was detected between the different levels for Hyflex CM (\(p>0.05\)).  
The percentage of untouched areas was similar between the two rotary systems (\(p>0.05\)) (Table 3). As reported in Figure 3, no significant differences in the distribution of untouched areas (i.e., green zone in the superimposed images) were appreciable between the samples prepared with 2 Shape and Hyflex CM.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{4}{c}{\(\Delta\)} \\ \hline
**Group** & \multicolumn{4}{c}{**MD Diameter**} \\ \hline  & **Coronal** & **Middle** & **Apical** & **Total** \\ \hline
**2 Shape** & 0.1356 \({}^{\text{a}}\)\(\pm\) 0.0128 & 0.1190 \({}^{\text{a}}\)\(\pm\) 0.0332 & 0.1110 \({}^{\text{a}}\)\(\pm\) 0.0293 & 0.1202 \(\pm\) 0.0342 \\ \hline
**Hyflex CM** & 0.1584 \({}^{\text{a}}\)\(\pm\) 0.0302 & 0.0734 \({}^{\text{b}}\)\(\pm\) 0.0268 & 0.0948 \({}^{\text{b}}\)\(\pm\) 0.0773 & 0.1123 \(\pm\) 0.0467 \\ \hline  & \multicolumn{4}{c}{**BL Diameter**} \\ \hline  & **Coronal** & **Middle** & **Apical** & **Total** \\ \hline
**2 Shape** & 0.0904 \({}^{\text{a}}\)\(\pm\) 0.0613 & 0.0710 \({}^{\text{a}}\)\(\pm\) 0.0262 & 0.1114 \({}^{\text{a}}\)\(\pm\) 0.0364 & 0.1219 \({}^{\text{a}}\)\(\pm\) 0.0268 \\ \hline
**Hyflex CM** & 0.0690 \({}^{\text{a}}\)\(\pm\) 0.0721 & 0.0458 \({}^{\text{a}}\)\(\pm\) 0.0207 & 0.0658 \({}^{\text{a}}\)\(\pm\) 0.0430 & 0.1089 \(\pm\) 0.0597 \\ \hline \hline \end{tabular} \(\Delta\) BL, variation in the maximum buccolingual dimension; \(\Delta\) MD, change in the maximum mesiodistal dimension. Different superscript letters indicate significant difference between the different root canal thirds of a same instrument. \({}^{\text{a}}\) Indicates significant difference between the two instruments in the same root canal third.  
\end{table}
Table 2: Mean and standard deviation (SD) of change (\(\Delta\)) in maximum mesiodistal and buccolingual dimensions considering each anatomical level and total root canal space.  
The 2 Shape increased significantly canal volume by 11.1% after brushing (\(p\) < 0.05) whereas Hyflex CM by 8.5% (\(p\) < 0.05) in percentages not statistically significant between the two files (\(p\) > 0.05) (Table 4).