RESUMO
Knowledge of existing situation in each region plays great role in order to prevent oral and dental diseases in people. Meanwhile, DMFT index is one of the best epidemiological indices in dentistry representing oral hygiene situation in society. So, this study was conducted in order to evaluate DMFT index in 12- years-old students of Qom City. This descriptive study was done cross - sectionally using interview, examination and questionnaire among 12- years- old students of Qom city. Considering WHO criteria, 300 samples were selected for the study and the effect of variables such as gender, the order of children in family, mother education, tooth brushing and the use of mouthwash on DMFT were evaluated. The data were analyzed by SPSS software Version 10. DMFT rate was achieved 2.28 +/- 2.1 while it was 2.87 +/- 2.03 in females and 2.72 +/- 2.18 in males. The existed difference [0.71] was not statistically significant [P>0.05]. DMFT in students who were used to tooth brushing was 2.6 +/- 2.05 and 3.28 +/- 2.15 in students not using toothbrushes, the difference was statistically significant [P<0.009]. Caries free rate was estimated 10.7% in the study [6% in females and 4.7% in males]. The study showed SCI of 5.15 +/- 1.45. Considering WHO criteria, the achieved DMFT index in Qom city was acceptable. According to the aim of WHO for the year of 2015 for 12 - years- old people [SCI of less than 3DMFT<1], it is necessary to perform special program for the purpose