矯正治療對前牙開咬或下顎後縮病患上呼吸道影響之三維分析

Abstract

Objectives: The aim of this study is to analyze morphological changes of upper airways in patients with anterior open bite after non-surgery orthodontic treatment. We superimposed airway structures in 2D cephalometric films and 3D MRI midsagittal films for measurements and tested the correlation between these two images. We also analyzed upper airway morphological changes of severe maxillo-mandibular bone discrepancy in patients with Angle Class II malocclusion after orthognathic surgery, and correlated airway structure changes and the amount of surgical displacement. Materials and Methods: Twelve non-obese (BMI<21) anterior open bite patients between age of 19 to 44 years old (mean age: 22.83±8.19 years old) were recruited for this study. Cephalometric radiographs and MRI scans before and after treatment were used to measure upper airway. Questionnaire was to assess changes of sleeping quality in patients. Upper airway was divided into two segments: retropalatal and retroglossal regions. Cephalometric analysis included bony structures, head position, hyoid bone position, and linear measurements, length, and areas of upper airways. MRI analysis included airway volume, minimal cross-sectional area, average cross-sectional area, length, width, and width/length ratio of upper airway, and tongue positions. We superimposed airway structures in cephalometric films on the corresponding linear segments to 3D axial sections. Paired t test was usd to analyze measurements before and after treatment. Pearson correlation coefficient was used to correlate airway structure between 2D and 3D images. P value less than 0.05 was considered statistically significant. Results: Mandibular plane angle and lower facial height significantly decreased, and AW2, IAS and RG areas significantly increased in cephalometric measurements after treatment. Retroglossal volume increased and retroglossal width/length ratio decreased significantly in MRI analysis. All other measurements were not significantly changed. About 2D and 3D images, there were no statistically significant correlations between measurements at those corresponding sites except AW2 linear measurement in 2D to AP length in MRI axial view (r=0.56, p=0.0430) Five patients stated their sleep quality improved after treatment in the questionnaire. No subjects felt their sleep quality got worse. Conclusion: Counterclockwise rotation of mandible after anterior bite closed by orthodontic treatment really changed airway morphology. Retroglossal volume significantly increased and airway shape became less elliptical after bite closure. All patients could keep or improve their sleep quality after treatment. Because the correlation between 2D and 3D variables was weak, cephalometric X-ray could not provide accurate information about the airway dimensions and is not recommended for assessing exact locations and the degree of constrictions of upper airway. Key words: anterior open bite; airway morphology; three dimensional analysis