# Three-Dimensional Change of Lip after Two-Jaw Surgery in Facial Asymmetry Using Facial Scanner
## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & & \(\Delta\)**U3Z-D** & \(\Delta\)**U3Z-ND** & \(\Delta\)**U6Z-D** & \(\Delta\)**U6Z-ND** & \(\Delta\)**MfZ-D** & \(\Delta\)**MfZ-ND** & \(\Delta\)**MeZ** \\ \hline \multirow{3}{*}{\(\Delta\)ChZ-D} & Pearson’s & & & & & & & \\  & correlation & 0.298 & 0.343 & 0.073 & 0.337 & \(-\)0.095 & 0.083 & 0.071 \\  & coefficient & & & & & & & \\  & \(p\) & 0.178 & 0.118 & 0.748 & 0.125 & 0.673 & 0.715 & 0.752 \\  & Pearson’s & & & & & & & \\  & correlation & 0.309 & 0.488 & \(-\)0.015 & 0.550 & \(-\)0.128 & 0.014 & 0.144 \\  & coefficient & & & & & & & \\  & \(p\) & 0.162 & 0.021 * & 0.949 & 0.008 ** & 0.571 & 0.951 & 0.522 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Correlation between the vertical changes in the cheilions (\(\Delta\)ChZ-D/ND) and the changes in other variables in the vertical direction. the findings reported by [PERSON] et al. [27]. Assuming that transverse lip asymmetry is the difference in the distance from the MSP to the Ch-D and Ch-ND in the transverse axis, the difference was significantly reduced after surgery, indicating that the asymmetry had improved (Table 4). Assuming that vertical lip asymmetry is the difference in the height of the Ch-D and Ch-ND in the vertical axis, this means that lip canting improved significantly after surgery (Table 4). One of the study methods to evaluate the change in lip cant after orthognathic surgery was to analyze the correlation between the amount of lip cant before and after surgery (e.g., the lip line cant changed from 3.18\({}^{\circ}\), 1.91 mm to 0.75\({}^{\circ}\), \(-\)0.25 mm after surgery) [8,22,28]. However, in these studies, it was difficult to evaluate whether the correction of the lip cant was due to the downward movement of the deviated-side cheliion or the upward movement of the non-deviated-side cheliion. Another method used to evaluate the change in lip cant was to analyze the change in the distance from the reference plane to the deviated- and non-deviated-side cheliions after orthognathic surgery [6,10,20]. In this study, the evaluation was performed according to this method. To investigate the factors affecting the vertical position of the cheliion (\(\Delta\)ChZ-D/ND) after orthognathic surgery, a correlation analysis was performed with the change in the hard tissue landmarks in each direction (transverse, anteroposterior, and vertical). As a result, it was found that there was no correlation between the transverse movement of the hard tissue and the \(\Delta\)ChZ-D/ND; there was a significant correlation between the mandibular differential setback and the downward movement of the cheliions; and there was a significant correlation between the impaction of the non-deviated side of the maxilla and the upward movement of the non-deviated side of the cheliion (Tables 6 and 7). Several studies evaluating the vertical movement of the cheliion after orthognathic surgery in patients with class III skeletal asymmetry showed that the cheliion moved downward according to the setback of the mandible [20,29,30]. In addition, [PERSON] et al. and [PERSON] et al. reported that there was significant downward movement of the deviated-side cheliion after orthognathic surgery in patients with class III facial asymmetry [6,10]. This study was conducted on patients diagnosed with skeletal class I or class III facial asymmetry who had a maxillary occlusal plane cant. To improve facial asymmetry, the impaction of the non-deviated side of the maxilla and the differential setback of the mandible were commonly performed; thus, the patients were analyzed together without dividing them into class I and class III groups. In this study, although there was a significant correction of the lip cant due to the decrease in the vertical difference between the deviated- and non-deviated-side cheliions after surgery, the average vertical change of the cheliion on each side was not statistically significant (Tables 3 and 4).