Orthodontic treatment need of 9, 12 and 15 year-old children according to the Index of Orthodontic Treatment Need and the Dental Aesthetic Index.

ABSTRACT

OBJECTIVE: To assess the differences in occlusal features in three cohorts at 9, 12 and 15 years of age, and compare orthodontic treatment need measured by the Dental Aesthetic Index (DAI) and Index of Orthodontic Treatment Need (IOTN). DESIGN: Cross-sectional study. SETTING: School of Dentistry, University of Valencia. SUBJECTS: A total of 1086 children 321 aged 9, 397 aged 12 and 368 aged 15. METHODS: Children were examined to measure their orthodontic treatment need according to IOTN and DAI. The main outcome measure was orthodontic treatment need according to the DAI and IOTN indices. RESULTS: Overbite and inter-incisal diastema were the occlusal features that presented significant differences between the three groups, diminishing with age. Treatment need according to the IOTN was 15.4% at 9 years, 20.9% at 12 years and 12.8% at 15 years. Treatment need according to DAI was 44.8% at 9 years, 21.7% at 12 years and 14.1% at 15 years. The diagnostic agreement between the two indices on the treatment need by age group was very low at 9 years (Kappa 0.18) and moderate at 12 and 15 years (Kappa 0.451 and 0.405, respectively). CONCLUSIONS: Orthodontic treatment need is greater in the mixed dentition and falls slightly as the child grows. The greatest variation in results between 9 and 15 years were found in relation to the DAI, which is consequently not recommended for use in the mixed dentition.