## 4 Discussion  
The purpose of this study was to investigate whether there was a change in the shape of IC and the relationship between the maxillary central incisor and IC after MARPE treatment. MARPE has been reported to induce not only maxillary transverse expansion but also three-dimensional changes in the zygomaticomaxillary complex [30]. We hypothesized that the morphology of the IC existing between the left and right maxilla would be changed through MARPE, which would affect the tooth-canal relationship. Using CBCT images, the regional morphologic changes of the IC in response to MARPE therapy were identified. These changes are comparable to the remodeling pattern and changes of the hard and soft tissues to different stimuli, including orthodontic tooth movement [31; 32; 33; 34; 35]. \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Measurements** & **T0** & **T1** & \(p\)**Value** \\ \hline \#11 Cr-\#21 Cr (\(n=30\)) & 9.74 \(\pm\) 1.44 & 9.43 \(\pm\) 0.80 & 0.258 \\ \hline \#11 Rm-\#21 Rm(L1) (\(n=20\)) & 2.88 \(\pm\) 1.06 & 4.86 \(\pm\) 1.84 & 0.000 *** \\ \hline \#11 Rm-\#21 Rm(L2) (\(n=20\)) & 3.25 \(\pm\) 1.15 & 5.44 \(\pm\) 1.75 & 0.000 *** \\ \hline \#11 Rm-\#21 Rm(L3) (\(n=20\)) & 3.95 \(\pm\) 1.12 & 5.84 \(\pm\) 1.66 & 0.000 *** \\ \hline \#11 Rt-\#21 Rt (\(n=30\)) & 7.17 \(\pm\) 1.55 & 8.94 \(\pm\) 1.68 & 0.000 *** \\ \hline \({}^{***}p<0.001\). & & & \\ \end{tabular}
\end{table} 
Table 4: Change in positional relationship between the maxillary central incisors after MARPE treatment (mean \(\pm\) standard deviation). \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Measurements** & \multicolumn{2}{c}{**L1**} & \multicolumn{4}{c}{**ANS mid**} & \multicolumn{4}{c}{**IC Bi**} \\ \cline{2-9}
**(\(n=10\))** & **T0** & **T1** & \(p\)**Value** & **T0** & **T1** & \(p\)**Value** & **T0** & **T1** & \(p\)**Value** \\ \hline IC ML width & 3.97 \(\pm\) 2.18 & 5.97 \(\pm\) 1.10 & 0.028 * & 3.52 \(\pm\) 1.52 & 5.70 \(\pm\) 1.28 & 0.000 *** & 4.85 \(\pm\) 1.53 & 6.73 \(\pm\) 1.56 & 0.000 *** \\ \hline IC LP width & 2.89 \(\pm\) 0.72 & 2.98 \(\pm\) 0.63 & 0.712 & 2.59 \(\pm\) 0.71 & 2.93 \(\pm\) 0.88 & 0.004 *** & 3.09 \(\pm\) 1.109 & 3.37 \(\pm\) 1.13 & 0.047 * \\ \hline \hline \end{tabular}  
* \(p<0.05\), ** \(p<0.01\), *** \(p<0.001\). \({}^{\dagger}\) Wilcoxon signed-rank test.  
\end{table} 
Table 3: Changes in IC dimensions after MARPE treatment in samples where the maxillary central incisors and the IC were vertically separated (mean \(\pm\) standard deviation). \begin{table}
\begin{tabular}{c c c} \hline \hline
**Measurements** & **T0** & **T1** & \(p\)**Value** \\ \hline IC volume (px) & 2269.6 \(\pm\) 838.7 & 3765.8 \(\pm\) 1096.8 & 0.000 *** \\ \hline IC volume (cm\({}^{3}\)) & 0.13 \(\pm\) 0.050 & 0.22 \(\pm\) 0.064 & 0.000 *** \\ \hline \hline \end{tabular}  
* \({}^{***}p<0.001\).  
\end{table} 
Table 5: Volume change in the IC after MARPE treatment (mean \(\pm\) standard deviation). The resolution of reconstructed CBCT images may vary based on a number of factors, including kVa, mA, scan time, reconstruction algorithms, the measurement location of the phantom, etc. [36; 37]. A 0.3-mm voxel size is often used with a considerably longer scan time for CBCT images with a broad field of view covering the whole face, as in our CBCT images, to provide higherquality images. CBCT images obtained for orthodontic reasons have been utilized as a reliable method to study orthodontically caused apical root resorption and changes in surrounding tissues, even if the limit of distance measurement is indicated to be twice the voxel size. Overall morphologic alterations, interroot distance, root canal distances, and the volume of the IC following MARPE treatment were all reliably detected in the research. The mediolateral, labiopalatal width, and volume of the IC increased clearly in all participants who received the MARPE treatment. It is notable that, to our knowledge, this is the first research to identify the remodeling possibilities of IC in response to MARPE treatment.