title: Extra-oral retraction mechanics: a review.
abstract: OBJECTIVE
  The literature relating the centres of resistance of the maxillary molars, the maxillary dental arch, and the maxilla to extra-oral retraction vectors intended for both orthodontic and orthopaedic effects, is reviewed. Conventional clinical wisdom concerning the different effects of cervical-, straight-, and high-pull vectors is questioned.
  
  
  CONCLUSIONS
  Published studies lack the rigorous design necessary for unequivocal interpretation.
authors.affiliation: Department of Orthodontics, Faculty of Dentistry, Khon Kaen University, Thailand. keigod@mail.kku.ac.th
authors.forename: Keith
authors.initials: K
authors.lastname: Godfrey
mesh_terms: D003799:Dental Stress Analysis; D005115:Extraoral Traction Appliances; D006801:Humans; D007180:Incisor; D008312:Malocclusion, Angle Class II / Q000628:therapy; D008437:Maxilla; D008963:Molar; D009971:Orthodontics, Corrective / Q000295:instrumentation*; D010349:Patient Compliance; D019415:Torque