Purpose The purpose of this study was to assess the quantitative three-dimensional (3-D) effects of orthognathic surgery on skeletal and pharyngeal airway morphology. Methods The patients were 22 Japanese females with mandibular prognathism. Ten patients underwent bilateral sagittal split ramus osteotomy and 12 underwent bilateral intraoral vertical ramus osteotomy without reduction glossoplasty. Spiral/helical computed tomography (CT) was performed before treatment and after orthognathic surgery. A volume-rendering technique was used to create 3-D CT images. Results The antero-posterior width, lateral width, cross-sectional area of the soft palate plane, and upper volume of the oropharyngeal airway decreased significantly following mandibular setback surgery. Significant positive correlations were found between changes in ANB, FH-NB angle, mandibular plane angle, Y-axis, the amount of mandibular setback and change in total height of the pharyngeal airway, and between changes in Co width and changes in distance and vertical height between the hyoid bone and the 3rd cervical vertebra. There was no significant correlation between surgical changes and the volume of the PAS after surgery. Conclusions Combined orthognathic–orthodontic treatment improved skeletal 3 deformities. Orthognathic surgery reduced the volume and the antero-posterior width of the pharyngeal airway of patients with such deformities.
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