Impacts of the COVID-19 Pandemic Exposure on Child Dental Caries: Difference-in-Differences Analysis

The impact of the coronavirus disease 2019 (COVID-19) pandemic on dental caries is unknown. We investigated the effect of the pandemic on child dental caries in Japan by comparing the increase in dental caries from fourth to sixth grade between two cohorts, COVID-19 exposed cohort and COVID-19 unexposed cohort, using difference-in-differences analysis. Longitudinal data that followed elementary school children in Adachi City, Tokyo, were analyzed. The analysis consisted of two cohorts: those who were in fourth grade in 2016 and sixth grade in 2018 (COVID-19 unexposed cohort, N = 399) and those who were in fourth grade in 2018 and sixth grade in 2020 (COVID-19 exposed cohort, N = 3,082). Children's dental caries were examined by school dentists. A difference-in-differences analysis, adjusting for time-variant variables, i.e., household socioeconomic status, children's oral health behavior, and caregivers' psychological distress, was performed. In fourth grade, the number of Decayed, Missing, and Filled permanent Teeth (DMFT) was not different between the COVID-19 unexposed and exposed cohorts (mean = 0.241 and 0.242, respectively). In sixth grade, DMFT increased by 0.067 in the COVID-19 unexposed cohort and 0.180 in the COVID-19 exposed cohort. The interaction term of grade and cohorts for caries by difference-in-differences analysis showed that dental caries among the COVID-19 exposed cohort showed a significant increase in the number of dental caries by 0.116 (95% confidence interval 0.015, 0.216) compared to the COVID-19 unexposed cohort. Child dental caries slightly increased after the pandemic. Studies with longer follow-ups are needed to evaluate the impact of the pandemic on child dental caries.