title: Changes in occlusal relationships in mixed dentition patients treated with rapid maxillary expansion. A prospective clinical study.
abstract: OBJECTIVE
  To prospectively measure occlusal changes in mixed dentition patients who underwent a standardized early expansion protocol.
  
  
  METHODS
  The treatment sample consisted of 500 patients who were assigned to three groups according to molar relationship: Class I (n = 204), end-to-end (n = 166), and Class II (n = 130). All patients were treated with a bonded rapid maxillary expander (RME) followed by a removable maintenance plate and a transpalatal arch. Mean age at the start of treatment was 8.8 years (T(1)), with a pre-phase 2 treatment cephalogram (T(2)) taken 3.7 years later. The control sample consisted of the cephalometric records of 188 untreated subjects (Class 1, n = 79; end-to-end, n = 51; Class II, n = 58).
  
  
  RESULTS
  The largest change in molar relationship was noted when the Class II treatment group (1.8 mm) was compared with the matched control group (0.3 mm). A positive change was seen in 81% of the Class II treatment group, with almost half of the group improving by > or = 2.0 mm. The end-to-end treatment group had a positive change of 1.4 mm, compared with a control value of 0.6 mm, and the Class I group of about 1 mm compared with controls, who remained unchanged (0.1 mm). Skeletal changes were not significant when any of the groups were compared with controls.
  
  
  CONCLUSIONS
  The expansion protocol had a significantly favorable effect on the sagittal occlusal relationships of Class II, end-to-end, and Class I patients treated in the early mixed dentition.
authors.affiliation: Department of Orthodontics and Pediatric Dentistry, School of Dentistry, The University of Michigan, Ann Arbor, Michigan 48109-1078, USA. mcnamara@umich.edu
authors.forename: James A
authors.initials: JA
authors.lastname: McNamara
authors.forename: Lauren M
authors.initials: LM
authors.lastname: Sigler
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Franchi
authors.forename: Susan S
authors.initials: SS
authors.lastname: Guest
authors.forename: Tiziano
authors.initials: T
authors.lastname: Baccetti
mesh_terms: D001499:Bayes Theorem; D002508:Cephalometry; D002648:Child; D016001:Confidence Intervals; D003818:Dentition, Mixed; D006801:Humans; D008311:Malocclusion, Angle Class I / Q000628:therapy*; D008312:Malocclusion, Angle Class II / Q000628:therapy*; D016011:Normal Distribution; D010155:Palatal Expansion Technique / Q000295:instrumentation; D011336:Probability; D011446:Prospective Studies