[Research methods in dentistry 10. Assessment of orthodontic treatment need].

Approximately one third of the Dutch population has an objective need for orthodontic treatment. Yet, patients mostly seek treatment because of aesthetic reasons. Recent social developments and the increased attention for aesthetics ask for ways to objectively measure treatment need. This is not only important because of the risks of orthodontic treatment, but also because of financial reasons. In this article indices to verify treatment need, i.e. the Index for Orthodontic Treatment Need (IOTN), de Dental Aesthetic Index (DAI) en de Index of Complexity, Outcome and Need (ICON), are discussed. All three indices seem to lead to a reduction of treatment need, especially in borderline cases. They can serve as 'neutral' instruments to discuss treatment need with patients and as instruments to allocate financial resources for orthodontic care.