Abstract
The strength of the evidence linking some common malocclusion traits (which are used as the basis for IOTN classification) with dental disease is reviewed. It is concluded that IOTN is not a reliable predictor of the potential impact of malocclusion on future dental health, and that alternative indices, which place greater emphasis on the aesthetic impairment and take account of patient perceptions, are more appropriate for assessing an individual's orthodontic treatment need.