title: [Cephalometric changes of the morphology of the symphysis after extraction in Angle Class II division 1 malocclusion patients].
abstract: OBJECTIVE
  To investigate the effects of extraction on the morphology of symphysis by evaluating the cephalograms of patients with Angle Class II division 1 malocclusion.
  
  
  METHODS
  A total of 45 subjects treated with Edegewise appliance were divided into 3 groups with extracting 4 first premolars(Group 1),extracting upper first premolars and lower second premolars (Group 2), and nonextraction (Group 3). Cephalograms were analyzed for all subjects, the morphology of the symphysis before and after treatment was measured. Paired Student's t test and ANOVA were performed via SPSS 11.5 software package.
  
  
  RESULTS
  In the two extraction groups, the thickness of symphysis at apex, B point decreased significantly (Group 1:0.60 mm, P<0.05;1.58 mm, P<0.01; Group 2:0.22 mm, P<0.05;1.16 mm, P<0.01) and the curvatura and inclination of symphysis also decreased(Group 1:1.91, P<0.05;4.69 degrees , P<0.01; Group 2:1.76, P<0.05;4.66 degrees P<0.01). There was no significant change in morphology of the symphysis in the nonextraction groups.
  
  
  CONCLUSIONS
  The thickness of symphysis at apex,and B point decreased significantly after the retraction of the lower incisors in the extraction groups, indicating that extraction treatment should be carefully selected in patients with a thin symphysis.
authors.affiliation: Department of Orthodontics, Hospital of Stomatology of Suzhou City, Suzhou 215005, Jiangsu Province, China.
authors.forename: Li-juan
authors.initials: LJ
authors.lastname: Song
authors.forename: Jun
authors.initials: J
authors.lastname: Wu
mesh_terms: D001641:Bicuspid; D002508:Cephalometry; D006801:Humans; D008312:Malocclusion, Angle Class II; D008334:Mandible / Q000033:anatomy & histology*; D014081:Tooth Extraction