title: Stability of Class II fixed functional appliance therapy--a systematic review and meta-analysis.
abstract: OBJECTIVE
  To systematically search for scientific evidence concerning the stability of treatment (Tx) results achieved by means of Class II fixed functional appliance therapy and to assess possible differences between appliances.
  
  
  METHODS
  An electronic search of databases and orthodontic journals was carried out (until December 2013), with supplemental hand searching. In addition to the names of all identified appliances, the term fixed functional was used in combination with each of the following search terms: long-term, post-Tx, relapse, retention, stability.
  
  
  METHODS
  To be included in the review, the articles had to contain clear data on: Class II Tx with a fixed functional appliance (>5 patients), post-Tx period ≥ 1 year, assessment of ANB angle, Wits appraisal, molar relationship, soft-tissue profile convexity excluding the nose, overjet and/or overbite.
  
  
  METHODS
  The literature search revealed 20 scientific investigations which corresponded to only two of the 76 identified appliances (Herbst and Twin Force Bite Corrector). As only one publication was found for the Twin Force Bite Corrector, a meta-analysis could only be performed for Herbst Tx. The data were extracted, pooled and weighted according to the number of patients in each study.
  
  
  RESULTS
  The mean values for post-Tx relapse (percentages relative to the Tx changes) were: ANB angle 0.2 degrees (12.4 per cent), Wits appraisal 0.5mm (19.5 per cent), sagittal molar relationship 1.2mm/0.1 cusp widths (21.8 per cent /6.5 per cent); soft-tissue profile convexity excluding nose less than 0.1 degrees (1.0 per cent), overjet 1.8mm (26.2 per cent), overbite Class II:1 1.4mm (44.7 per cent), overbite Class II:2 1.0mm (22.2 per cent).
  
  
  CONCLUSIONS
  The scientific evidence concerning the stability of Tx results is inexistent for most fixed functional appliances for Class II correction except for Herbst appliance Tx. Even if the evidence level of most included studies is rather low, good dentoskeletal stability without clinically relevant changes was found for most variables.
authors.affiliation: Department of Orthodontics, University of Giessen, Germany niko.c.bock@dentist.med.uni-giessen.de.
authors.forename: Niko C
authors.initials: NC
authors.lastname: Bock
authors.affiliation: Department of Orthodontics, University of Giessen, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: von Bremen
authors.affiliation: Department of Orthodontics, University of Giessen, Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: Ruf
mesh_terms: D002508:Cephalometry / Q000379:methods; D006801:Humans; D008312:Malocclusion, Angle Class II / Q000628:therapy*; D008334:Mandible / Q000473:pathology; D008437:Maxilla / Q000473:pathology; D008963:Molar / Q000473:pathology; D017289:Orthodontic Appliances, Functional; D057887:Overbite / Q000628:therapy; D012008:Recurrence; D016896:Treatment Outcome
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