title: Does rapid maxillary expansion affect nasopharyngeal airway? A prospective Cone Beam Computerised Tomography (CBCT) based study.
abstract: OBJECTIVE
  There is limited literature discussing the three dimnesional (3D) impact of rapid maxillary expansion (RME) on upper airway. The purpose of this prospective Cone Beam Computerised Tomography (CBCT) based study is to assess the immediate 3D effects and to correlate the volumteric changes in the upper naspharyngeal airway spaces secondary to RME.
  
  
  METHODS
  Seventeen participants (8 male, 9 female, with a mean age of 12.6 ± 1.8 years), who required RME for the management of narrow maxillary arch, were recruited for this study. The prescribed expansion regimen was quarter turn (0.25 mm), twice a day until over-expansion was achieved. The mean period for the active phase was 14 days with a range of 12-21 days. Pretreatment (T1) and immediate post-expansion (T2) CBCT images were obtained and then processed using ITK snap and OnDemand3D softwar packages. Paired t-test and Interclass Correlation Coefficient (ICC) were used to assess the reproducibility of the measurements, student t-test (P < 0.05) and Pearson Correlation Coefficient (PCC) were applied to evaluate the volumetric changes in the nasopharyngeal airway spaces, linear dentolaveolar changes and correlate these changes.
  
  
  RESULTS
  Though, the data of one patient was excluded from the study, owing to major differences (>5 degrees) in the head and neck posture between T1 and T2 CBCT scans, the study' findings shows that bonded RME is an effective dentoalveolar expander in growing patients (P= 0.01) with an average expansion of 3.7 mm and 2.8 mm in males and females respectively. Likewise, the upper nasopharynx (UNP) expanded significantly (15.2% in males and 12% in females). In comparison, the upper retropalatal space (URP) was significantly reduced, by almost one sixth of its original volume, more in males than females, 11.2% and 2.8% respectively. A strong direct correlation between the maxillary sinus volumetric changes, and between appliance expansion and dentoalveolar expansion were evident (PCC = 0.86, 0.75, respectively). There was also a moderate correlation between changes in the UNP and URP spaces.
  
  
  CONCLUSIONS
  RME was found to be an effective dentoalveolar expander and significantly augment the UNP and minimize the URP space. A similar comparative clinical study with long-term follow-up would be beneficial in accurately deteremining the clinical impact of RME on the airway and breathing as well as the stability of these effects.
authors.affiliation: Orthodontic Department, Sydney Dental Hospital, University of Sydney, Sydney, NSW, Australia; Medical Devices Unit, NHS Greater Glasgow and Clyde, Glasgow, UK. Electronic address: dr_muzian@hotmail.com.
authors.forename: Mohammed
authors.initials: M
authors.lastname: Almuzian
authors.affiliation: Medical Devices Unit, NHS Greater Glasgow and Clyde, Glasgow, UK.
authors.forename: Xiangyang
authors.initials: X
authors.lastname: Ju
authors.affiliation: Orthodontic Department, Glasgow Dental Hospital and School, MVLS College, University of Glasgow, Glasgow, UK.
authors.forename: Anas
authors.initials: A
authors.lastname: Almukhtar
authors.affiliation: Oral & Maxillofacial Surgery, Glasgow Dental Hospital & School, MVLS College, University of Glasgow, Glasgow, UK.
authors.forename: Ashraf
authors.initials: A
authors.lastname: Ayoub
authors.affiliation: Deportment of Dental Public Health, School of Dentistry, Faculty of Medical and Human Science, University of Manchester, Manchester, UK.
authors.forename: Lubna
authors.initials: L
authors.lastname: Al-Muzian
authors.affiliation: Orthodontic Department, Glasgow Dental Hospital and School, MVLS College, University of Glasgow, Glasgow, UK.
authors.forename: Jim P
authors.initials: JP
authors.lastname: McDonald
mesh_terms: D000293:Adolescent; D002648:Child; D054893:Cone-Beam Computed Tomography; D005260:Female; D006801:Humans; D008297:Male; D008437:Maxilla / Q000000981:diagnostic imaging* / Q000601:surgery; D008443:Maxillary Sinus / Q000000981:diagnostic imaging* / Q000601:surgery; D009305:Nasopharynx / Q000000981:diagnostic imaging* / Q000601:surgery; D010155:Palatal Expansion Technique; D010159:Palate / Q000000981:diagnostic imaging* / Q000601:surgery; D011446:Prospective Studies
keywords: Airway space; CBCT; ITK snap software; OnDemand3D software; Rapid maxillary expansion