title: [Effect of high pull J hook headgear on root resorption during orthodontic treatment].
abstract: OBJECTIVE
  The purpose of this study was to evaluate the effect of high pull J hook headgear(HPHG) on root resorption of maxillary incisors during orthodontic treatment.
  
  
  METHODS
  Sixty female adolescent subjects who had finished orthodontic treatment were selected. They were either Class I or Class II division I cases treated with standard edgewise appliances. Half of the patients(30 cases) had an additional HPHG to assist upper anterior teeth retraction. They were matched to the other 30 cases with age and type of malocclusion. Panoramic radiographs taken before and after the orthodontic treatment were used to evaluate the degree of root resorption on upper incisors. Chi(2) test was used for statistical analysis.
  
  
  RESULTS
  The incidence of root resorption on upper incisors was significantly increased after orthodontic treatment in both HPHG and non-HPHG groups (P<0.01). Compared to the non-HPHG group, more teeth in HPHG group showed moderate or severe root resorption (P<0.01). Some cases even encountered extremely severe root resorption.
  
  
  CONCLUSIONS
  A combination of HPHG might lead to more severe root resorption on maxillary incisors during orthodontic treatment.
authors.affiliation: Department of Orthodontics, Ninth People'Hospital, School of Stomatology, Shanghai Second Medical University, Shanghai 200011, China. chenwei1969@hotmail.com
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
authors.forename: Rong-jing
authors.initials: RJ
authors.lastname: Chen
mesh_terms: D000293:Adolescent; D005115:Extraoral Traction Appliances; D005260:Female; D006801:Humans; D012391:Root Resorption / Q000473:pathology*