Objectives:The aim was to investigate the severity of untreated dental caries among Nepalese schoolchildren and its association with their body mass index (BMI) using IOTF, WHO and Nepalese growth reference systems.Methods: This school-based clinical cross-sectional study was conducted with three WHO index age groups (5-to 6-, 12-and 15-year-olds) in 18 out of 75 districts of Nepal, selected using stratified random sampling. A total of 1135 schoolchildren were included in the study. A validated structured questionnaire was used to assess the children's oral hygiene practices and dietary habits. Clinical oral examinations investigated the status of untreated dental caries in primary and permanent teeth (dt/DT) along with its consequences (pufa/PUFA). Later, the grade of severity of untreated dental caries (GUDC) was determined using both dt/DT and pufa/PUFA. Height (cm), weight (kg), waist circumference (cm) and hip circumference (cm) were measured, and the body mass index (BMI), waist-to-hip ratio (WHR) and waist-to-height ratio (WHtR) were calculated. The findings were presented as proportions, and the chisquare test was performed to compare differences between groups. Generalized linear mixed models with random effects assessed the association between the severity of untreated dental caries and the BMI.Results: According to the IOTF, WHO and Nepalese growth reference systems, the overall proportions of children with a low BMI were 38.6%, 15.4% and 12.8%, and those with a high BMI were 7.9%, 4.6% and 8.4%, respectively. Untreated dental caries was common among the youngest age group and those with infrequent tooth brushing habits or frequent consumption of sweet bakery products, sweets or candy, or tea with sugar. Neither a low nor a high BMI was associated either with dt + DT or with pufa + PUFA, after adjusting for confounders. However, both a low and a high BMI (all three references) were associated with the severity of dental caries or GUDC. Conclusion:Regardless of the growth reference system used, children with either low or high BMI may be at risk of developing untreated dental caries lesions and related consequences. Both underweight and overweight/obese and dental caries share common risk factors, mostly dietary. Preventive and intervention approaches/ strategies such as behavioural and dietary modifications should be implemented to improve both children's oral health and their nutrition in Nepal. | 347KARKI et Al.