M Markazi Moghadam
A Moghimbeigi
F Jafari

Statement of the Problem: Malocclusion is a developmental problem, which results in social, psychological and functional problems for patients. Purpose: The aim of this study was to evaluate the need for orthodontic treatment using the Index of Orthodontic Treatment Need (IOTN) among the ۱۱‒۱۴-year-old students of Hamadan schools in ۲۰۱۰ and to find the correlation between Dental Health Component (DHC) and Aesthetic Component (AC). Materials and Methods: A cross-sectional descriptive study was conducted on ۷۲۱ students who had not undergone orthodontic treatment. The subjects were randomly selected (۳۶۱ males and ۳۶۰ females). DHC was assessed by a calibrated examiner. AC was determined using ۱۰ standard photographs shown to students. Data were analyzed using chi-squared test to determine differences in treatment needs between subgroups of the subjects. The two components were evaluated using Spearman's correlation and kappa tests. Results: According to DHC, of ۷۲۱ cases surveyed, ۴۸.۷% had mild need for treatment; ۲۵.۱% had moderate need; and ۲۶.۲% had definite need. The most frequently observed malocclusion was contact point displacement. According to AC, ۸۸.۱% of students had mild need for treatment; ۷.۸% had moderate need and ۴.۲% had definite need. Comparison of DHC and AC showed no agreement between them (kappa value=۰.۰۶۹). Conclusion: According to DHC of the IOTN, approximately one-third of the population had a definite need for orthodontic treatment, and contact point displacement was the most prevalent malocclusion. Although IOTN is a valid screening tool, patient's perception of orthodontic treatment does not always correlate with professional assessment. According to the result of this study, it is advisable not to use AC instead of DHC in epidemiological studies.