Effect of orthodontic treatment on the upper airway volume in adults.

INTRODUCTION: The aim of this study was to examine the effects of orthodontic treatment with and without extractions on the anatomic characteristics of the upper airway in adults. METHODS: For this retrospective study, the pretreatment and posttreatment cone-beam computed tomography scans of 74 adult patients meeting defined eligibility criteria were analyzed. Imaging software was used to segment and measure upper airway regions including the nasopharynx, the retropalatal, and retroglossal areas of the oropharynx, as well as the total airway. The Wilcoxon signed rank test was used to compare volumetric and minimal cross-sectional area changes from pretreatment to posttreatment. RESULTS: The reliability values were high for all measurements, with intraclass correlation coefficients of 0.82 or greater. The volumetric treatment changes for the extraction and nonextraction groups were as follows: total airway, 1039.6 +/- 3674.3 mm(3) vs 1719.2 +/- 4979.2 mm(3); nasopharynx, 136.1 +/- 1379.3 mm(3) vs -36.5 +/- 1139.8 mm(3); retropalatal, 412.7 +/- 3042.5 mm(3) vs 399.3 +/- 3294.6 mm(3); and retroglossal, 412.5 +/- 1503.2 mm(3) vs 1109.3 +/- 2328.6 mm(3). The treatment changes in volume or minimal cross-sectional area for all airway regions examined were not significantly (P >0.05) different between the extraction and nonextraction groups. CONCLUSIONS: Orthodontic treatment in adults does not cause clinically significant changes to the volume or the minimally constricted area of the upper airway. These results suggest that dental extractions in conjunction with orthodontic treatment have a negligible effect on the upper airway in adults.