title: Volumetric upper airway changes after rapid maxillary expansion: a systematic review and meta-analysis.
abstract: BACKGROUND
  Although Rapid Maxillary Expansion (RME) has been used for over a century, its effect on upper airways has not yet adequately been assessed in an evidence-based manner.
  
  
  OBJECTIVE
  To investigate the volumetric changes in the upper airway spaces following RME in growing subjects by means of acoustic rhinometry, three-dimensional radiography and digital photogrammetry.
  
  
  METHODS
  Literature search of electronic databases and additional manual searches up to February 2016.
  
  
  METHODS
  Randomized clinical trials, prospective or retrospective controlled clinical trials and cohort clinical studies of at least eight patients, where the RME appliance was left in place for retention, and a maximum follow-up of 8 months post-expansion.
  
  
  METHODS
  After duplicate data extraction and assessment of the risk of bias, the mean differences and 95 per cent confidence intervals (CIs) of upper airway volume changes were calculated with random-effects meta-analyses, followed by subgroup analyses, meta-regressions, and sensitivity analyses.
  
  
  RESULTS
  Twenty studies were eligible for qualitative synthesis, of which 17 (3 controlled clinical studies and 14 cohort studies) were used in quantitative analysis. As far as total airway volume is concerned patients treated with RME showed a significant increase post-expansion (5 studies; increase from baseline: 1218.3mm3; 95 per cent CI: 702.0 to 1734.6mm3), which did not seem to considerably diminish after the retention period (11 studies; increase from baseline: 1143.9mm3; 95 per cent CI: 696.9 to 1590.9mm3).
  
  
  CONCLUSIONS
  However, the overall quality of evidence was judged as very low, due to methodological limitations of the included studies, absence of untreated control groups, and inconsistency among studies.
  
  
  CONCLUSIONS
  RME seems to be associated with an increase in the nasal cavity volume in the short and in the long term. However, additional well-conducted prospective controlled clinical studies are needed to confirm the present findings.
  
  
  BACKGROUND
  None.
  
  
  BACKGROUND
  Australian Society of Orthodontics Foundation for Research and Education Inc.
authors.affiliation: Discipline of Orthodontics, Faculty of Dentistry, University of Sydney, Sydney Dental Hospital, Sydney South West Area Health Service, Australia.
authors.forename: Lloyd M
authors.initials: LM
authors.lastname: Buck
authors.affiliation: Discipline of Orthodontics, Faculty of Dentistry, University of Sydney, Sydney Dental Hospital, Sydney South West Area Health Service, Australia.
authors.forename: Oyku
authors.initials: O
authors.lastname: Dalci
authors.affiliation: Discipline of Orthodontics, Faculty of Dentistry, University of Sydney, Sydney Dental Hospital, Sydney South West Area Health Service, Australia.
authors.forename: M Ali
authors.initials: MA
authors.lastname: Darendeliler
authors.affiliation: Departments of Orthodontics.|Oral Technology, School of Dentistry, University of Bonn, Germany.
authors.forename: Spyridon N
authors.initials: SN
authors.lastname: Papageorgiou
authors.affiliation: Discipline of Orthodontics, Faculty of Dentistry, University of Sydney, Sydney Dental Hospital, Sydney South West Area Health Service, Australia.|Department of Oral Surgery, Implantology and Dental Radiology, School of Dentistry, Aristotle University of Thessaloniki, Greece.
authors.forename: Alexandra K
authors.initials: AK
authors.lastname: Papadopoulou
mesh_terms: D006801:Humans; D009296:Nasal Cavity / Q000473:pathology; D010155:Palatal Expansion Technique; D011446:Prospective Studies; D012137:Respiratory System / Q000473:pathology*; D012189:Retrospective Studies; D023842:Rhinometry, Acoustic / Q000379:methods