title: [A comparative study of clinical application of two types appliances for maxillary molar distalization].
abstract: OBJECTIVE
  The aim of this study is to evaluate advantages and disadvantages of two types of appliances for maxillary molar distalization.
  
  
  METHODS
  Totally, 28 patients with class II malocclusion resulting from molars shifting mesially were treated using two different molar distalization methods, including using removable and fixed appliances. An intra-oral removable acrylic appliance with headgear for extra-oral traction resulted in tipping the maxillary first molars distally. The modified rapid helix expansion appliance (MRHEA), which consisted of bands, anchorage teeth, Nance palatine bases, helix bars and connecting rods, made the maxillary first molars move parallel distally.
  
  
  RESULTS
  The desired efforts were gained in 7 or 9 months by using removable appliances, but only 2 or 2.5 months if using MRHEA. The treatment results of using removable appliances were dependent on patients' cooperation, however, the method of using fixed appliance overcame some shortcomings of other molar distalization techniques, and this appliance would not lead to the distal inclination of the crown of the shifted teeth.
  
  
  CONCLUSIONS
  These two methods could convert the class II molar relationship to class I. The MRHEA can save much chair-side time, and shorten the period of treatment, move molars distally parallel.
authors.affiliation: Department of Orthodontics, Stomatological Hospital of Foshan.
authors.forename: Z
authors.initials: Z
authors.lastname: Wang
authors.forename: C
authors.initials: C
authors.lastname: Huang
authors.forename: H
authors.initials: H
authors.lastname: Zhou
authors.forename: Z
authors.initials: Z
authors.lastname: Liu
mesh_terms: D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D008312:Malocclusion, Angle Class II / Q000628:therapy*; D008963:Molar; D016382:Orthodontic Appliance Design; D009967:Orthodontic Appliances; D014087:Tooth Movement Techniques / Q000295:instrumentation / Q000379:methods*