Background Dental fluorosis is a major public health problem in 17 states of India. Earlier studies reported that sorghum {a type of millet, (jowar)} consumption interacts with fluoride in the body and enhances fluorosis.

Objectives This study was carried out to explore the potential association between sorghum consumption and severity of dental fluorosis.

Methods A community based case control study was carried out in villages having different fluoride levels (high, medium and low) in drinking water in Davangere, India. 352 school Children (12–15 years, male 58 %) with severe grades of dental fluorosis classified by Thylstrup & Fejerskov Index (scores 4–9) were selected as cases. 428 school children (12–15 years, male 48.8%) with no dental fluorosis were selected randomly from the same area as controls. Exposure ascertainment of jowar consumption was done by 24-h diet recall and food frequency questionnaire. Logistic regression analysis was done using SPSS version 17.

Results Children who consumed jowar had 2.67 times more chance of getting severe dental fluorosis compared to those who did not (OR 2.67, CI 1.98 to 3.62). The ORs for jowar consumption and dental fluorosis were 1.59, 3.18 and 3.76 at each stratum, for low, medium and high fluoride villages respectively. The Mantel-Haenszel OR was 2.58 (p value=0.001) which was similar to crude OR. The test of homogeneity (Breslow test) showed p value=0.05.

Conclusions Sorghum consumption modifies the effect of fluoride in occurrence of severity of dental fluorosis in this population.