Background and purpose: Severe early childhood caries (S-ECC) are amongst the major problems of oral health in children. The purpose of this study was to determine any relationship between S-ECC and body mass index (BMI) in children (2-4 years of age).

Materials and methods: In this case-control study, 300 S-EEC infected and 300 S-ECC free children were randomly selected from Tehran kindergartens. Data was collected by examinations and demographic data, different variables including height, weight, BMI, nutrition type, milk consumption were recorded in a checklist. Data were subjected to Chi-square and Logistic regression tests.

Results: Gender and nutrition type in the first two years of life, milk consumption and having special eating habits were significantly associated with developing S-ECC (p-value<0/05). Breast feeding and formula feeding were reported in 40.5% of boys and 51.2% of girls, respectively. The boys (71.9%) and girls (80.4%) used dietary supplements and 70.6% of boys and 72.4% of girls consumed sweet snacks. The subjects were similar in terms of weight, age and height while the DMFT index in girls was higher than that in males (p<0.05). The BMI values were not significantly different between the two groups (p<0.05).

Conclusion: No significant relationship was noted between body mass index and severe early child hood caries.