title: Effects of rapid maxillary expansion in hyperdivergent patients.
abstract: BACKGROUND
  This retrospective cohort study was performed to evaluate the skeletal and dental changes in the short and long terms in hyperdivergent patients treated with rapid maxillary expansion and fixed appliances.
  
  
  METHODS
  The sample consisted of 143 patients who had rapid maxillary expansion with a Haas-type expander followed by edgewise therapy. Two groups were established: a normal vertical dimension group (mandibular plane angle >20° and <27°; n = 52) and a hyperdivergent group (mandibular plane angle ≥27°; n = 91). Lateral cephalograms were taken before treatment (average age, 11.5 years in both groups) and after fixed appliance therapy (average age, 14.3 years in both groups). Subjects who exhibited opening or closing in the mandibular plane angle during treatment greater than 1.5° (opening group, n = 23; closing group, n = 26) were followed in the long term (average age, 20.3 years). Longitudinal changes in the different groups were evaluated statistically as well as the prevalence rates of hyperdivergent patients in the opening and closing groups.
  
  
  RESULTS
  No significant differences in treatment effects were found in any sagittal or vertical dentoskeletal variables examined. The long-term evaluation of the patients at 5 or more years posttreatment showed no significant skeletal changes. The prevalence rate of hyperdivergent patients in the opening group was not significant.
  
  
  CONCLUSIONS
  The results of this study indicate that rapid maxillary expansion can be carried out successfully in patients with increased vertical dimensions without detrimental effects on the vertical skeletal relationships. Thus, an increased mandibular plane angle is not a contraindication for rapid maxillary expansion therapy.
authors: Graduate Program in Orthodontics, Department of Orthodontics and Pediatric Dentistry, University of Michigan, Ann Arbor, MI 48109, USA.
authors: Matthew W
authors: MW
authors: Lineberger
authors: James A
authors: JA
authors: McNamara
authors: Tiziano
authors: T
authors: Baccetti
authors: Thomas
authors: T
authors: Herberger
authors: Lorenzo
authors: L
authors: Franchi
mesh_terms: D000293:Adolescent; D002508:Cephalometry / Q000379:methods; D002648:Child; D002680:Chin / Q000473:pathology; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007180:Incisor / Q000473:pathology; D008137:Longitudinal Studies; D008297:Male; D008310:Malocclusion / Q000145:classification / Q000628:therapy*; D008334:Mandible / Q000473:pathology; D008437:Maxilla / Q000473:pathology; D008963:Molar / Q000473:pathology; D009295:Nasal Bone / Q000473:pathology; D016382:Orthodontic Appliance Design; D010155:Palatal Expansion Technique / Q000295:instrumentation; D012189:Retrospective Studies; D012658:Sella Turcica / Q000473:pathology; D014087:Tooth Movement Techniques / Q000295:instrumentation; D016896:Treatment Outcome; D014716:Vertical Dimension