title: A review of the oral health-related evidence that supports the orthodontic treatment need indices.
abstract: OBJECTIVE
  To date, there is no evidence-based method of quantification for malocclusion. Consequently, how deviant occlusal traits should be scored and weighted relative to one another is a matter of serious debate. Orthodontic Treatment Need Indices (OTNI) use the subjective opinion of the experts, as their foundation, to define the pathological boundaries (cut-offs) of occlusal traits. This paper reviews the evidence relating malocclusions or deviated occlusal traits to oral health problems, and investigates if this evidence supports the cut-off points and the rationale used for OTNI.
  
  
  METHODS
  The relevant cited studies and reviews from the MEDLINE, Web of Science, Scopus, Cochrane databases, and scientific textbooks were used. The citation rate was confirmed by using the Google Scholar.
  
  
  RESULTS
  So far, the evidence for harmful effects of deviated occlusal traits on oral health is either lacking or exists as cross-sectional (mostly) and longitudinal (a few and primarily short-term) studies. When an association was reported between a deviated occlusal trait and an oral health problem, either the strength of that association was weak, or due to methodological issues, findings were not conclusive. Consequently, establishing a cause and effect relationship is difficult. Further, commonly used OTNI do not record a full spectrum of occlusal traits, and relating their ranking or scoring systems to the available evidence is difficult. Therefore, there is little evidence to suggest that individuals with a high need (high score), as measured by OTNI, will necessarily put at risk their oral health if they turn down orthodontic therapy.
  
  
  CONCLUSIONS
  OTNI have a role in the epidemiology and can be used for resource planning, but their predictive value to detect the future objective functional deficits or oral health problems is questionable. OTNI will need revalidation over time with emerging research findings.
authors.affiliation: Honorary Fellow of the University of Warwick, Warwick Dentistry, Warwick Medical School, Coventry, UK. farahani@faraortho.com
authors.forename: Ali
authors.initials: A
authors.lastname: Borzabadi-Farahani
mesh_terms: D055094:Evidence-Based Dentistry; D006801:Humans; D061326:Index of Orthodontic Treatment Need; D008310:Malocclusion / Q000175:diagnosis*; D009909:Oral Health