title: [Comparative study on the apical root resorption between self-ligating and conventional brackets in extraction patients].
abstract: OBJECTIVE
  To explore whether orthodontic light force with self-ligating brackets can reduce the amount of external apical root resorption (EARR).
  
  
  METHODS
  Thirty patients with Class I or II crowding malocclusion were selected. Four first premolars of all patients were extracted in orthodontic treatment. 15 patients were treated with self-ligating brackets (Damon 3MX) and 15 patients with conventional ligation brackets, respectively. Patients in two groups were comparable in gender, age, crowded degree and malocclusion classification at the commencement of treatment. EARR of the maxillary and mandible incisors was evaluated on panoramic radiographs and models taken before and after treatment, and measured in millimeters. Student's t test was performed using SPSS19.0 software package.
  
  
  RESULTS
  Overall, no difference was found in the amount of EARR between the two groups. The amount of EARR in maxillary central incisor was (2.05±1.51) mm in Damon group and (2.08±1.21) mm in conventional group(P=0.973>0.05); (1.77±1.01) mm in maxillary lateral incisor in Damon group and (1.91±1.59) mm in conventional group(P=0.848>0.05); (2.06±1.62) mm in mandibular central incisor in Damon group and (1.98±1.50) mm in conventional group(P=0.926>0.05); (1.94±1.45) mm in mandibular lateral incisor in Damon group and (1.84±1.17) mm in conventional group(P=0.888>0.05).
  
  
  CONCLUSIONS
  No difference should be expected for root resorption between self-ligating and conventional brackets in orthodontic extraction treatment.
authors.affiliation: Department of Orthodontics, the Affiliated Hospital of Medical College, Qingdao University, Qingdao 266003, Shandong Province, China. dentistlxq@163.com
authors.forename: Xin-qiang
authors.initials: XQ
authors.lastname: Liu
authors.forename: Xiao-lei
authors.initials: XL
authors.lastname: Sun
authors.forename: Qian
authors.initials: Q
authors.lastname: Yang
authors.forename: Cun-hui
authors.initials: CH
authors.lastname: Fan
authors.forename: Xiu-juan
authors.initials: XJ
authors.lastname: Chen
mesh_terms: D001641:Bicuspid; D006801:Humans; D007180:Incisor; D008310:Malocclusion; D008334:Mandible; D008437:Maxilla; D016910:Orthodontic Brackets; D012391:Root Resorption