Orthodontic treatment outcomes in the long term: findings from a longitudinal study of New Zealanders.

The aim of this study was to use a health services research (HSR) approach to examine the longer-term outcomes of orthodontic treatment. Participants in a longstanding population-based New Zealand cohort study (the Dunedin Multidisciplinary Health and Development Study) were allocated to one of four malocclusion severity categories on the basis of orthodontic data collected at age 12. The outcome of that care by age 26 was evaluated using the key indicators of equity (was it fair?); efficacy (did it work?); effectiveness (did it work in the longer term?); and safety (was it associated with a greater subsequent experience of caries, periodontal disease, or tooth loss?). Data were available for 452 Study members, of whom 56.2% were in the minor/none category, 29.0% were in the definite category, 10.2% were in the severe category, and 4.6% were in the handicapping treatment-need category. No clear differences in treatment uptake by socioeconomic status were apparent, and the proportion treated increased across the malocclusion severity categories, as did the proportion that showed an improvement following treatment. By age 26 a difference between those who had and those who had not been treated was evident, with the percentage of those rating their dental appearance as above average increasing with increasing severity of the age-12 orthodontic treatment need. This was also true for the percentage that considered their orthodontic treatment to have been successful. There were no significant differences in caries experience, periodontal disease occurrence, or tooth loss between those who had and had not been treated by age 26. This study has found the equity, efficacy, effectiveness, and safety of orthodontic treatment in the Dunedin cohort to be acceptable.