Sex, ethnicity and area-level deprivation have a greater impact on dental caries than body mass index (BMI), according to a near whole population cross-sectional study. Data for 582, 820 children were extracted from the national B4 School Check screening programme between July 2010 and June 2021, of whom 98.2% had valid BMI and oral health records. Median age of the children was 4.3 years, 48.7% were female, 23.4% and 12.8% were identified as Māori and Pacific, respectively, and 24.4% lived in the most deprived areas of New Zealand. Overall, 14.2% had dental caries identified. After adjustment for age, sex, ethnicity and area level deprivation, a significant flattened S-shaped association was found between dental caries and BMI; those with lower sex-specific BMI-for-age z-scores had lower predicted probabilities of dental caries. However, large differences in predicted probabilities were observed between different sex, ethnicity and area-level deprivation groups.
