An introduction to indices of malocclusion.

Orthodontic indices have been used for many years to assess the severity of a patient's malocclusion and hence determine the need for treatment. Two indices--the Index of Orthodontics Treatment Need (IOTN) and the Peer Assessment Rating (PAR) Index--have recently been developed. The use of indices is likely to become more widespread in the future so that more uniformity is achieved in assessing need for treatment and its success. This article describes how the two indices are applied.