title: Sagittal and vertical effects of rapid maxillary expansion in Class I, II, and III occlusions.
abstract: OBJECTIVE
  To evaluate and compare the skeletal vertical and sagittal effects of the Hyrax expander in Class I, II, and III patients.
  
  
  METHODS
  One hundred and eighty-three patients (91 females, 92 males) with a mean age of 8.7 years and with maxillary bilateral cross-bite and maxillary hypoplasia were analyzed retrospectively. They were divided into three groups according to their skeletal class. Sixty-five patients were skeletal Class I, 55 were skeletal Class II, and 63 were skeletal Class III. For each patient a lateral cephalogram was obtained before treatment and at the end of the retention period. Changes in the groups during the observation period were calculated, compared, and statistically analyzed with a t-test.
  
  
  RESULTS
  In terms of vertical effects, a statistically significant increase in the anterior vertical dimension was observed only in Class III patients. No statistically significant changes were observed in the posterior vertical dimension in any of the groups. In terms of sagittal effects, in Class I patients the maxilla and the mandible moved forward, but not in a statistically significant way, and the ANB angle showed a statistically significant decrease, but its change was less modified. In Class II patients the maxilla moved forward, but not in a statistically significant way, while the mandible moved forward in all of the patients in a statistically significant manner. The ANB decreased, statistically improving the skeletal classification. In Class III patients the maxilla moved forward in a statistically significant manner; the mandible showed a downward and backward rotation, improving the skeletal classification.
  
  
  CONCLUSIONS
  The data obtained in this study permit us to confirm that rapid maxillary expansion can be used in all of the skeletal classes with good vertical and sagittal results.
authors.affiliation: Department of Orthodontics, IRCCS Cà Granda–Ospedale Maggiore Policlinico, University of Milan, Italy.
authors.forename: Giampietro
authors.initials: G
authors.lastname: Farronato
authors.forename: Lucia
authors.initials: L
authors.lastname: Giannini
authors.forename: Guido
authors.initials: G
authors.lastname: Galbiati
authors.forename: Cinzia
authors.initials: C
authors.lastname: Maspero
mesh_terms: D002508:Cephalometry; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D008311:Malocclusion, Angle Class I / Q000628:therapy*; D008312:Malocclusion, Angle Class II / Q000628:therapy*; D008313:Malocclusion, Angle Class III / Q000628:therapy*; D017289:Orthodontic Appliances, Functional; D010155:Palatal Expansion Technique / Q000295:instrumentation*; D012189:Retrospective Studies; D016896:Treatment Outcome; D014716:Vertical Dimension