To explore the relationship between body mass index (BMI) and oral health among school aged children in Guangzhou.

A cross-sectional study of 7-12 years old students′ physical fitness and health status was carried out using stratified random cluster sampling method from September 2014 to December 2014 according to the "2014 national student physical fitness and health research plan". Oral examination was performed according to the scheme and the DMFT score number of deciduous teeth and permanent teeth (dmft/DMFT) were recorded. In the meanwhile, the height and weight calculation of BMI was measured. In accordance with the gender, age and BMI of the tested children, the caries prevalence rate and mean DMFT were calculated. The marasmus index was evaluated on the basis of the "Chinese children of 6-19 years old adolescents BMI screening range" and the overweight and obesity were evaluated on the basis of the "China school-age children and adolescents for screening overweight and obesity body mass index (BMI) classification standards". Accordingly, the subjects were divided into 4 groups: marasmus group, the normal body weight group, overweight group and obesity group. By means of t test, chi square test and analysis of variance statistics methods, the correlation between BMI and caries was analyzed. The data of 7, 9 and 12 years old urban and rural Han students were studied by BMI.

The number of tested children of age 7, 9, 12 was 2903 in total, and the caries rate was 32.3% (937/2903) with the caries prevalence rate 3.7% (108/2903) . The mean caries of each subject was 1.27, and the permanent teeth mean caries index was 0.09. The detection rates of the four groups were 10.8% (313/2903) , 72.9% (2116/2903) , 9.2% (267/2903) and 7.2% (209/2903) respectively. Comparing with normal weight children with marasmus group and control group, the difference of prevalence rate of dental caries of deciduous teeth was statistically significant (χ²= 25.43, P= 0.000) . There was a significant correlation between marasmus and deciduous teeth caries.

Marasmus and deciduous teeth caries occurrence are correlated. Improving the nutritional status of children helps reduce the caries degree. There was no statistically significant association between overweight/obesity and dental caries in children.