title: Changes in temporomandibular joint disc position and form following Herbst and fixed orthodontic treatment.
abstract: OBJECTIVE
  To determine the changes in the position and form of the temporomandibular joint articular disc in adolescents with Class II division 1 malocclusion and mandibular retrognathism treated with the Herbst appliance (phase I) and fixed orthodontic appliance (phase II).
  
  
  METHODS
  Thirty-two consecutive adolescents went through phase I of treatment and 23 completed phase II. The temporomandibular joints were evaluated qualitatively by means of magnetic resonance images at the beginning of treatment (T1), during phase I (T2), at the end of phase I (T3), and at the end of phase II (T4).
  
  
  RESULTS
  Significant changes in disc position were not observed with the mouth closed between T1 x T3 (P = .317), T3 x T4 (P = .287), or T1 x T4 (P = .261). At T2, on average, the disc was positioned regressively. With the mouth open, no difference was observed between T1 x T3 (P = .223) or T1 x T4 (P = .082). We did observe a significant difference between T3 x T4 (P < .05). Significant changes in the disc form were found with the mouth closed between T1 x T2 (P < .001) and T2 x T3 (P < .001).
  
  
  CONCLUSIONS
  At the end of the two-phase treatment, in general terms, the position and form of the initial articular discs were maintained; however, in some temporomandibular joints some seemingly adverse effects were observed at T4.
authors.affiliation: Department of Orthodontics, Santa Cecília University, Santos, São Paulo, Brazil. luisaidar@uol.com.br
authors.forename: Luís Antônio de Arruda
authors.initials: LA
authors.lastname: Aidar
authors.forename: Gladys Cristina
authors.initials: GC
authors.lastname: Dominguez
authors.forename: Hélio K
authors.initials: HK
authors.lastname: Yamashita
authors.forename: Márcio
authors.initials: M
authors.lastname: Abrahão
mesh_terms: D000293:Adolescent; D002648:Child; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008312:Malocclusion, Angle Class II / Q000628:therapy*; D008335:Mandibular Condyle / Q000473:pathology; D016382:Orthodontic Appliance Design; D009967:Orthodontic Appliances; D017289:Orthodontic Appliances, Functional; D016910:Orthodontic Brackets; D010155:Palatal Expansion Technique / Q000295:instrumentation; D011446:Prospective Studies; D063173:Retrognathia / Q000628:therapy*; D013701:Temporal Bone / Q000473:pathology; D013704:Temporomandibular Joint / Q000473:pathology; D019224:Temporomandibular Joint Disc / Q000473:pathology*