Three-dimensional evaluation of changes in the upper airway, natural head position and hyoid bone position in skeletal Class Ⅲ patients after bimaxillary surgery

Abstract

Objective To assess short- and long-term changes in the upper airway, natural head position and hyoid bone position in skeletal Class Ⅲ patients after bimaxillary surgery. Methods In this retrospective study, the cone-beam computed tomography(CBCT) of skeletal Class Ⅲ patients was taken before surgery(T0), 3 months after surgery(T1) and 2 years after surgery(T2). Three-dimensional images were created to assess postoperative changes and the correlation between the upper airway, natural head position and hyoid bone was analyzed. Results Thirty skeletal Class Ⅲ patients(13 men and 17 women) who underwent bimaxillary surgery with a mean(SD)age of 21 years(a range of 17-30 years)were evaluated. A significant decrease was observed in the volume of palatopharynx, glossopharynx and total airway after T1 and T2. There was a significant correlation between changes in the position of the mandible and changes in the volume of the upper airway(P<0.05). The NSL/OPT angle and the NSL/CVT angle were greater after T1 and T2. The change in the NSL/CVT angle was positively correlated with the change in palatopharyngeal and glossopharyngeal volume(P<0.05). Conclusion Bimaxillary surgery may cause a decrease in upper airway volume, an increase in the cranio-cervical angle, and a downward and backward movement of the hyoid bone. Changes in the cranio-cervical angle may cause changes in the upper airway.

Keywords

• |upper airway|skeletal class ⅲ|bimaxillary surgery|cone-beam computed tomography