Predicting orthodontic treatment need: reliability and validity of the Demand for Orthodontic Treatment Questionnaire.

Objectives: To identify key measures in predicting orthodontic treatment need and to propose a self-assessment instrument that improves treatment need assessment.

Subjects and methods: The study included 150 randomly selected 13-year-olds. A set of measures linked to a previous study on daily life impact of malocclusion was processed, resulting in an instrument, the Demand for Orthodontic Treatment Questionnaire (DOTQ), which was analysed regarding dimensionality, reliability and validity. Dental Health Component of the Index of Orthodontic Treatment Need (IOTN-DHC) grading, representing professionally assessed treatment need, were collected from dental records. The instrument's ability to predict treatment need was tested by randomly splitting the dataset into two subgroups, using multiple regression to predict DHC in one of the groups and the prediction equation to calculate predicted DHC in the other. The outcomes were then correlated to detect the predictive power of the DOTQ, and thereby the validity of the prediction.

Results: The DOTQ-measures were reliable and highly inter-correlated. A high, significant correlation was found between assessed and predicted treatment need for the subgroups (r = 0.59 and 0.49), confirming the validity of the prediction. Independent variables (the measures) explained 47 per cent (R = 0.69) of the variance in treatment need. Four measures contributed significantly to the prediction, with Treatment Demand being the most powerful predictor.

Limitations: The age group and response rate may raise some questions regarding the generalizability of the findings.

Conclusions: The DOTQ is able to predict treatment need as assessed by orthodontic consultants. Its incorporation in the treatment need assessment process will acknowledge patients' self-perceived impact of malocclusion.