Comparing and contrasting two orthodontic indices, the Index of Orthodontic Treatment need and the Dental Aesthetic Index.

This article compares and contrasts two orthodontic indices, the Index of Orthodontic Treatment Need (IOTN), and the Dental Aesthetic Index (DAI). Both contain esthetic and clinical criteria. Both accept the premise that a significant benefit of orthodontic treatment is improved esthetics and, by inference, social and psychological well-being. Both have as their goal the identification of children most in need of orthodontic treatment subsidized by public funds. The first part of this article describes the IOTN, its development, reliability, and validity. The second section describes the DAI, its development, reliability, and validity. The third part of the article compares and contrasts the indices. There are a number of differences between the IOTN and the DAI. In the IOTN, the esthetic component is a separate instrument from the dental health component. The unique aspect of the DAI is its linking of people's perceptions of esthetics with anatomic trait measurements by regression analysis to produce a single score obviating the need, as in the IOTN, for two separate scores that cannot be combined. Both components of the IOTN have only three grades, "no need," "borderline need," and "definite need." The IOTN cannot rank order cases with greater or lesser need for treatment within grades. In contrast, DAI scores can be rank ordered on a continuous scale and can differentiate cases within severity levels. With the IOTN, about a third of British schoolchildren would be found eligible for treatment in public programs. Providing publicly funded orthodontic care to as many as a third of the schoolchildren would not be feasible in the United States.