title: Upper Airway Changes after Orthodontic Extraction Treatment in Adults: A Preliminary Study using Cone Beam Computed Tomography.
abstract: OBJECTIVE
  Whether the orthodontic treatment with premolar extraction and maximum anchorage in adults will lead to a narrowed upper airway remains under debated. The study aims to investigate the airway changes after orthodontic extraction treatment in adult patients with Class II and hyperdivergent skeletal malocclusion.
  
  
  METHODS
  This retrospective study enrolled 18 adults with Class II and hyperdivergent skeletal malocclusion (5 males and 13 females, 24.1 ± 3.8 years of age, BMI 20.33 ± 1.77 kg/m2). And 18 untreated controls were matched 1:1 with the treated patients for age, sex, BMI, and skeletal pattern. CBCT images before and after treatment were obtained. DOLPHIN 11.7 software was used to reconstruct and measure the airway size, hyoid position, and craniofacial structures. Changes in the airway and craniofacial parameters from pre to post treatment were assessed by Wilcoxon signed rank test. Mann-Whitney U test was used in comparisons of the airway parameters between the treated patients and the untreated controls. Significant level was set at 0.05.
  
  
  RESULTS
  The upper and lower incisors retracted 7.87 mm and 6.10 mm based on the measurement of U1-VRL and L1-VRL (P < 0.01), while the positions of the upper and lower molars (U6-VRL, and L6-VRL) remained stable. Volume, height, and cross-sectional area of the airway were not significantly changed after treatment, while the sagittal dimensions of SPP-SPPW, U-MPW, PAS, and V-LPW were significantly decreased (P < 0.05), and the morphology of the cross sections passing through SPP-SPPW, U-MPW, PAS, and V-LPW became anteroposteriorly compressed (P <0.001). No significant differences in the airway volume, height, and cross-sectional area were found between the treated patients and untreated controls.
  
  
  CONCLUSIONS
  The airway changes after orthodontic treatment with premolar extraction and maximum anchorage in adults are mainly morphological changes with anteroposterior dimension compressed in airway cross sections, rather than a decrease in size.
authors.affiliation: Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing, PR China.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing, PR China.
authors.forename: Gui
authors.initials: G
authors.lastname: Chen
authors.affiliation: Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing, PR China.
authors.forename: Weiran
authors.initials: W
authors.lastname: Li
authors.affiliation: Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing, PR China.
authors.forename: Tianmin
authors.initials: T
authors.lastname: Xu
authors.affiliation: Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing, PR China.
authors.forename: Xuemei
authors.initials: X
authors.lastname: Gao
mesh_terms: D000293:Adolescent; D000328:Adult; D056151:Airway Remodeling / Q000502:physiology*; D001641:Bicuspid / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D016022:Case-Control Studies; D054893:Cone-Beam Computed Tomography; D005260:Female; D006801:Humans; D006928:Hyoid Bone / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D007180:Incisor / Q000000981:diagnostic imaging / Q000601:surgery; D008297:Male; D008312:Malocclusion, Angle Class II / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D008437:Maxilla / Q000000981:diagnostic imaging / Q000601:surgery; D008963:Molar / Q000000981:diagnostic imaging / Q000601:surgery; D009960:Oropharynx / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D012189:Retrospective Studies; D014081:Tooth Extraction