Introduction: Molar Incisor Hypomineralization (MIH) is a kind of developmental enamel defect with multifactorial etiology that causes different dental complication. So, many studies  have been done on this subject. The aim of this study was the evaluation of relationship between Molar Incisor Hypomineralization (MIH) with body mass index (BMI) and dental caries index (DMFT) in 7-11 year old children in Yazd City.

Methods: In this descriptive analytic study, 645 children between 7 to 11 years old in Yazd City were selected via randomized cluster sampling and were examined in the schools. EAPD and mDDE criteria were used for detection of MIH and the extension in teeth. Body mass index and permanent dental caries were evaluated based on the World Health Organization (WHO) criteria. 40 children were examined for BMI and dental caries as an unaffected group. The mean value was analyzed with Mann Whitney test and the result was significant (P<0.05).

Results: Out of 645 children, 154 were affected by MIH, 16 children (10.38%) were underweight, 13 children (8.44%) were overweight, 3 children (1.94%) were obese and 122 children (79.22%) had normal weight. BMI in the affected group and control group were 16.01 and 15.76, respectively. The difference of BMI between MIH group and control was not statistically significant (P=0.81). DMFT in children with MIH was 2.09 and in the control group was 1.1, respectively that means in affected group  there was a statistical difference than the control group (P=0.001).

Conclusions: Children who suffering from MIH often have normal BMI and they have more decay in their permanent teeth.