title: [Modified retention elements of removable reverse headgear appliances].
abstract: OBJECTIVE
  Retention elements were added in the removable reverse headgear appliances in order to achieve better treatment effects of skeletal Class III malocclusion.
  
  
  METHODS
  Eighteen patients who needed treatments with reverse headgear appliances were randomly and equally divided into two groups with traditional type of retention elements (T group) and modified type of retention elements (M group) respectively. For the modified type appliances, an adams clasp was added in the position of central incisors on the basis of the traditional type. The minimum dislocating force for both types was measured with the same forcemeter in the first and second visit, respectively. The occurrence of dislocation caused by traction was recorded during the visits of the first three months.
  
  
  RESULTS
  The M group showed significantly greater retention than the T group. The minimum dislocating force for M group was larger in the first and second visit (P<0.01, P<0.001). Furthermore, during the first three months, two times of dislocation occurred in M group while it was nine times for T group, indicating great difference in retention (P< 0.05).
  
  
  CONCLUSIONS
  Adding an adams clasp in the position of upper central incisors could effectively prevent the downward dislocation of the appliance when traction force was applied. Accordingly, the therapeutic efficacy was greatly improved.
authors.affiliation: Department of Orthodontics, The Third Affiliated Hospital of Neimenggu Medical College, Baotou 014010, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.forename: Xiao-Feng
authors.initials: XF
authors.lastname: Fan
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhao
authors.forename: Jing-Hui
authors.initials: JH
authors.lastname: Zhang
authors.forename: Zhi-He
authors.initials: ZH
authors.lastname: Zhao
mesh_terms: D005115:Extraoral Traction Appliances; D005260:Female; D006801:Humans; D007180:Incisor; D008297:Male; D008312:Malocclusion, Angle Class II; D008313:Malocclusion, Angle Class III; D014070:Tooth; D014087:Tooth Movement Techniques