title: [A pilot study on changes of posterior available spaces in mandible dentitions for adolescents between the ages of 11 and 20 years in Chengdu area].
abstract: OBJECTIVE
  The purpose of this study was to study the changes of available spaces of posterior arch segments in mandible dentitions (ASPAS) from ages of 11 to 20 years, which would provide information on normal growth and development of the dental arches in teenagers in Chengdu area.
  
  
  METHODS
  The data were derived from systematically collected preorthodontic lateral cephalograms of 526 patients, including 232 males and 294 females from the Orthodontic Department of West China College of Stomatology, Sichuan University during the period of 1999-2000 (aged 11-20 years). The values of ANB angle, FH-MP, ASPAS were obtained using the cephalometric analysis. Afterwards, the growth changes of ASPAS from the subjects and their correlations with age, gender, angle malocclusion types and vertical skeletal patterns were analyzed.
  
  
  RESULTS
  ASPAS was related to age and class II angle malocclusion. Though gender was not associated with ASPAS, significant differences in curves of ASPAS were found between males and females. The growth changes of ASPAS in the patients with skeletal Class III malocclusion were more obvious than in patients with Class I and II malocclusion.
  
  
  CONCLUSIONS
  Our results reveal that significant differences were demonstrated in growth change values in posterior available spaces of patients with different races and angle malocclusion types.
authors.affiliation: Department of Orthodontics, West China College of Stomatology, Sichuan University, Chengdu 610041, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.forename: Zhihe
authors.initials: Z
authors.lastname: Zhao
authors.forename: Chufeng
authors.initials: C
authors.lastname: Liu
mesh_terms: D000293:Adolescent; D044466:Asian People; D003724:Dental Arch / Q000033:anatomy & histology / Q000473:pathology*; D003817:Dentition; D005260:Female; D006801:Humans; D008297:Male; D008310:Malocclusion / Q000000981:diagnostic imaging / Q000473:pathology*; D008334:Mandible / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000473:pathology*; D009971:Orthodontics, Corrective; D010865:Pilot Projects; D011859:Radiography; D012016:Reference Values