Cone-beam computed tomography evaluation of short- and long-term airway change and stability after orthognathic surgery in patients with Class III skeletal deformities: bimaxillary surgery and mandibular setback surgery.

The purpose of this study was to evaluate the volumetric change of the upper airway space in 36 Class III patients who had undergone bimaxillary surgery or isolated mandibular setback, and, further, to analyse the relation between post-surgical stability and airway change using cone-beam computed tomography (CBCT). A three-dimensional (3D) CBCT examination was performed at three stages: T0 (before surgery), T1 (an average of 4.6 months after surgery), and T2 (an average of 1.4 years after surgery). The results showed that the volumes of the oropharyngeal and hypopharyngeal airways decreased significantly 4.6 months post-surgery in the mandibular setback group (p<0.05), and these diminished airways had not recovered 1.4 years post-surgery. In the bimaxillary surgery group, the volume of the oropharyngeal airway also decreased. A Spearman correlation analysis showed that the anteroposterior length of the hypopharyngeal area had a correlation with post-surgical stability in the isolated mandibular surgery group, and that the cross-sectional area of the nasopharynx was correlated with maxillary relapse only in the bimaxillary surgery group (p<0.05).

The assessment of the short- and long-term changes in the condylar position following sagittal split ramus osteotomy (SSRO) with rigid fixation.

The purpose of this study was to compare the short- and long-term changes in condylar position related to the glenoid fossa, and skeletal and occlusal stability after orthognathic surgery. All of the study patients were assessed by cone-beam computed tomography images for condylar rotational changes and anteroposterior position in the pre-surgery, post-surgery and post-retention period. The condylar positions were evaluated on three planes: axial, coronal and sagittal. In the skeletal and occlusal measurements, there was no significant difference between the post-surgery group and the post-retention group. After sagittal split ramus osteotomy (SSRO), the condyle on the axial plane rotated inward (P < 0.05) and maintained during the post-retention period. In the anteroposterior condylar position related to the glenoid fossa, the condyles had changed from the anterior position in the pre-surgery group to a concentric position in the post-surgery group and then returned to the anterior position in the post-retention groups. These results suggested that the changed anteroposterior condylar position in the glenoid fossa after SSRO with rigid fixation had moved from a concentric to anterior position for post-retention period.