title: Changes of pharyngeal airway size and hyoid bone position following orthodontic treatment of Class I bimaxillary protrusion.
abstract: OBJECTIVE
  To test the hypothesis that the sagittal position of the anterior teeth has no effect on pharyngeal airway dimension or hyoid bone position and to investigate the influence of orthodontic retraction of the anterior teeth on each section of pharynx and hyoid position.
  
  
  METHODS
  Forty-four Class I bimaxillary protrusion adults, treated with preadjusted appliances and maximum anchorage after extraction of four premolars, were divided into two groups according to their vertical craniofacial skeletal patterns. Pretreatment and posttreatment variables were compared using paired t-test, and the relationship between pharyngeal airway size and dentofacial variables was analyzed using Pearson correlation coefficient. The changes of pharyngeal airway size and hyoid position after treatment were compared between two groups using independent t-test.
  
  
  RESULTS
  Upon retraction of the incisors, the upper and lower lips were retracted by 2.60 mm and 3.87 mm, respectively. The tip of upper incisor was retracted by 6.84 mm and lower incisor retracted by 4.95 mm. There was significant decrease in SPP-SPPW, U-MPW, TB-TPPW, V-LPW, VAL, C3H, and SH (P < .05). No statistically significant different changes were observed in the dentofacial structures, pharyngeal airway, and hyoid position between the two groups after the treatment. There was a significant correlation between the retraction distance of lower incisor and the airway behind the soft palate, uvula, and tongue.
  
  
  CONCLUSIONS
  The pharyngeal airway size became narrower after the treatment. Extraction of four premolars with retraction of incisors did affect velopharyngeal, glossopharyngeal, hypopharyngeal, and hyoid position in bimaxillary protrusive adult patients.
authors.affiliation: Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing, PR China; and Department of Orthodontics, Dental Research Institute, College of Stomatology, Nanjing Medical University, Nanjing, PR China.
authors.forename: Qingzhu
authors.initials: Q
authors.lastname: Wang
authors.forename: Peizeng
authors.initials: P
authors.lastname: Jia
authors.forename: Nina K
authors.initials: NK
authors.lastname: Anderson
authors.forename: Lin
authors.initials: L
authors.lastname: Wang
authors.forename: Jiuxiang
authors.initials: J
authors.lastname: Lin
mesh_terms: D000293:Adolescent; D000328:Adult; D056151:Airway Remodeling; D002508:Cephalometry; D005260:Female; D006801:Humans; D006928:Hyoid Bone / Q000033:anatomy & histology; D007180:Incisor / Q000473:pathology; D008297:Male; D008311:Malocclusion, Angle Class I / Q000473:pathology / Q000628:therapy*; D009971:Orthodontics, Corrective / Q000379:methods*; D010614:Pharynx / Q000033:anatomy & histology*; D012189:Retrospective Studies; D016896:Treatment Outcome; D014716:Vertical Dimension; D055815:Young Adult