# The Effects of Chewing Exercises on Masticatory Function after Surgical Orthodontic Treatment
## 4 Discussion  
This study evaluated chewing patterns, oral function, and condylar position before and after orthognathic surgery with a chewing exercise in patients with skeletal class III SSRO. SSRO is widely performed for surgical orthodontic treatment of patients with jaw deformities. [PERSON] (1986) reported that changes in the mandible after SSRO included external and superior displacement of the proximal bone fragment within a short timeframe,  
Figure 11: Changes in chewing patterns between T1 and T2. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c c} \hline \hline  & \multicolumn{6}{c}{**Exercise Group (n = 10)**} & \multicolumn{6}{c}{**Control Group (n = 19)**} \\ \cline{2-13}  & \multicolumn{2}{c}{X} & \multicolumn{2}{c}{Y} & \multicolumn{2}{c}{Z} & \multicolumn{2}{c}{\(\emptyset\)} & \multicolumn{2}{c}{X} & \multicolumn{2}{c}{Y} & \multicolumn{2}{c}{Z} & \multicolumn{2}{c}{\(\emptyset\)} \\ \cline{2-13}  & **Mean** & **SD** & **Mean** & **SD** & **Mean** & **SD** & **Mean** & **SD** & **Mean** & **SD** & **Mean** & **SD** & **Mean** & **SD** \\ \hline Lp (mm) & \(-0.1\) & 0.4 & 0.1 & 0.1 & 0.1 & 0.5 & & & \(-0.2\) & 1.3 & 0.2 & 1.0 & 0.4 & 0.7 & & & \\ Cp (mm) & \(-0.1\) & 0.4 & 0.1 & 0.5 & 0.2 & 0.6 & & & \(-0.7\) & 2.3 & 0.1 & 2.5 & \(-0.2\) & 0.9 & & & \\ An (mm) & 0.1 & 0.8 & \(-0.6\) & 3.4 & \(-0.5\) & 2.3 & & & \(-0.9\) & 2.8 & 2.4 & 2.2 & \(-1.9\) & 4.0 & & & \\ Condylar & & & & & & & & & 3.0 & 1.1 & & & & & & & 3.0 & 3.9 \\ angle (\({}^{\circ}\)) & & & & & & & & & & & & & & & & & \\ \hline \hline \end{tabular}  
* Lp: Lateral point Cp: Coronoid process An: Antegional notch.  
\end{table} 
Table 3: Comparison between exercise group and control group of proximal bone fragment and axial condylar angle between T1 and T2. which induced the external, superior, and internal rotation of the condyle, resulting in bone remodeling from the external to the anterosuperior condyle. Thus, after SSRO, changes in the proximal bone fragments may cause unpredictable reactions in the mandibular position and occlusion. Several studies have reported that there were no significant differences between the preoperative chewing cycle duration or peak velocity and the corresponding postoperative values [25; 26]. However, [PERSON] et al. [16] reported that after and before orthognathic surgery, the chewing pattern changed in approximately 50% of patients from the narrow type (chopping) to the broader (grinding) type, and the condylar position also changed due to condylar resorption. Furthermore, [PERSON] et al. [17] reported that the chewing pattern changed from chopping to grinding after SSRO. The results of our study's control group are consistent with those reported previously [16; 17]. A previous study suggested that chewing exercises after orthognathic surgery improve masticatory efficiency and bite force [27]. [PERSON] et al. [28] stated that the setback of the mandible by SSRO improves the activity of the masticatory muscles. It was also reported that improved occlusal contact increases bite force [29]. Our previous study in Japan suggested that a chewing exercise for grown-up children facilitates an increase in oral function and changes in chewing patterns [30]. The results of the present study are similar to those of the previous studies of chewing exercises. The masticatory pattern changed to the normal type in 60% of the patients and remained unchanged from the reversed and crossover type in 40% of the patients. Three of the four patients with no change had a crossbite molar occlusion on their first visit. The results suggest that longer or more demanding chewing exercises are needed to change masticatory movements. In contrast, 21.0% of the patients in the control group showed a change to the normal type. This may be a natural adaptation due to the changes in morphology. A more detailed study is needed to determine what does and what does not improve with chewing exercises. [PERSON] et al. [16] suggested that patients with a broader chewing pattern after SSRO undergo condylar remodeling.