RESUMEN
AIM: To assess orthodontic treatment need in a Tehran high school population. METHODS: The Dental Health Component (DHC) of the Index of Orthodontic Treatment Need (IOTN) was used by 21 trained examiners to estimate the orthodontic treatment need in 5200 Tehran high school students. The children, between 14 and 16 years of age, attended 84 high schools in 21 educational areas in Tehran and the neighbouring city of Rey. Children who had had orthodontic treatment and those who had not been treated were assessed. Children under treatment were excluded. Major components of the DHC were recorded. RESULTS: When the DHC is considered, 2 per cent of Tehran school children showed 'Extreme need', 18 per cent 'Severe need', 23 per cent 'Moderate need', 37 per cent 'Little need' and 20 per cent had 'No need' of orthodontic treatment. In those needing treatment (Grades 4 and 5) common deviations were hypodontia, contact point displacements, crossbites and increased overjet. A small number of the subjects (N=36) who had received orthodontic treatment required further treatment. Of these, 18 subjects (50 per cent) had hypodontia, 10 subjects (28 per cent) had contact point displacements and 4 subjects (11 per cent) had increased overjet. CONCLUSION: Twenty per cent of Tehran high school students needed orthodontic treatment (IOTN Grades 4 and 5).