The objective of the present study was to identify the zygomaticomaxillary suture (ZMS) in a three-dimensional plane using cone-beam computed tomography (CBCT) and elucidate the relationships between maxillofacial size / morphology and plane directions. This study included 90 Japanese adult women, with a mean age of 27.07 ± 8.70 years. CBCT was used to identify the ZMS in a three-dimensional plane, represented by three points on the ZMS and defined mathematically by the three-dimensional coordinates of these points. The plane directions were evaluated based on the angles between the right and left ZMS planes and between the Frankfort horizontal plane and ZMS planes. In addition, several maxillofacial angles and distances were measured using CBCT, and the distance ratios were calculated. The correlations between the ZMS angles and maxillofacial measurements and distance ratios were evaluated using Pearson’s correlation coefficient. The angle between the right and left ZMS planes weakly correlated with zygomatic arch width ( r=-0.21). In addition, the ratio between the maxillary vertical distance and width and that between the maxillary vertical distance and anteroposterior distance also weakly correlated with the angle between the right and left ZMS planes ( r=0.24～0.25). The ZMS plane directions may correlate with maxillofacial morphology.

　　We used cone beam computed tomography data at the time of orthodontic treatment planning (T1) and at the completion of preoperative orthodontic treatment (T2) to quantify the changes in the morphology of the mandibular symphysis and elucidate the relevant factors. Additionally, using three-dimensional finite element analysis model (3D-FEM), we aimed to verify the mechanical behavior of the mandibular symphysis when applying orthodontic force to the mandibular anterior teeth.
　　This study included 45 patients with skeletal mandibular prognathism. The following six angles were evaluated in the measured areas: FMA, ANB angle, gonial angle, Y-axis angle, IMPA at T1 and only IMPA at T2. The distance of the measurement indicated the amount of change in bone morphology. In 3D-FEM, orthodontic force was added as the weight, and the stress distribution was calculated.
　　Statistical analysis suggested that the FMA, IMPA change, treatment period, and ANB angle affected the morphological changes. Additionally, no changes in the bone morphology were observed near the base of the mandibular symphysis, and the 3D-FEM yielded the same results.
　　In conclusion, changes in the bone morphology caused by surgical orthodontic treatment are limited to the area surrounding the roots of the teeth.