title: Associations between orthodontic treatment need and oral health-related quality of life among young adults: does it depend on how you assess them?
abstract: OBJECTIVE
  To determine the association between orthodontic treatment need (OTN) and oral health-related quality of life (OHRQoL).
  
  
  METHODS
  A cross-sectional study involving 273 young adults seeking orthodontic care. OHRQoL was assessed by the short-form Oral Health Impact Profile (OHIP-14) and United Kingdom oral health-related quality of life measure (OHQoL-UK). Study casts were assessed for OTN by: Dental Aesthetic Index (DAI), Index of Orthodontic Treatment Need (IOTN)-Aesthetic Component (IOTN-AC) and Dental Health Component (IOTN-DHC) and Index of Complexity, Outcome and Need (ICON). Variations in OHIP-14 and OHQoL-UK were determined with respect to OTN, and the magnitude of differences was calculated (effect size: ES).
  
  
  RESULTS
  There were significant but weak correlations between occlusal indices scores and OHIP-14 scores (P<0.05, r<0.3) and between occlusal indices scores and OHQoL-UK scores (P<0.05, r<0.4). The magnitude of the statistical difference in OHQoL-UK scores was moderate to large with respect to OTN (ES: 0.36-0.87) and largest when DHC (ES=0.87) and ICON (ES=0.74) were used. The magnitude of the statistical difference in OHIP-14 scores was relatively lower (ES: 0.21-0.69), but also greatest when DHC and ICON were used to determine OTN (ES 0.69 and 0.50, respectively).
  
  
  CONCLUSIONS
  Orthodontic treatment need was associated with OHRQoL. The magnitude of the statistical difference between those with and without an orthodontic treatment need was larger when OHRQoL was assessed using OHQoL-UK compared to OHIP-14. DHC and ICON were more useful indices in identifying greater differences in OHRQoL with respect to orthodontic treatment need.
authors.affiliation: Orthodontics, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: Zhijian
authors.initials: Z
authors.lastname: Liu
authors.forename: Colman
authors.initials: C
authors.lastname: McGrath
authors.forename: Urban
authors.initials: U
authors.lastname: Hägg
mesh_terms: D000293:Adolescent; D000328:Adult; D003430:Cross-Sectional Studies; D003753:Dental Health Surveys; D004955:Esthetics, Dental / Q000523:psychology; D005260:Female; D006801:Humans; D008297:Male; D008310:Malocclusion / Q000628:therapy; D020380:Needs Assessment; D009909:Oral Health; D009970:Orthodontics / Q000706:statistics & numerical data; D011788:Quality of Life / Q000523:psychology*; D055815:Young Adult