Trends and age-period-cohort effect on dental caries prevalence from 2008 to 2019 among Brazilian preschoolers.

This study aimed to evaluate trends in the prevalence of dental caries in preschool children and associated factors considering different time variations. This is a time series study performed using data from three cross-sectional studies with pre-school children from southern Brazil in 2008, 2013 and 2019. This children group was born between the years of 2003 to 2018. Dental caries was evaluated by decayed, missing and filled deciduous teeth (dmft index). Demographic, socioeconomic, behavioural and psychosocial variables were also collected. Chi-square test for trends and a hierarchical age-period-cohort (HAPC) analysis using multilevel Poisson regression model for testing the associations between predictor variables and dental caries experience were used. A total of 1,644 pre-school children participated in all surveys. There was a significant difference in caries experience considering all APC effects. The prevalence of dental caries was 25.0% in 2008, 16.3% in 2013, and 19.4% in 2019 (p < 0.01) and no statistical difference was observed. An age effect showed that older children were more likely to experience dental caries. Considering the cohort effect, there is a significant difference between the generations, mainly between 2003 and 2018. Household income, use of dental services, and parent's perception of child oral health were associated with dental caries experience no matter the time variation. Despite recent declines in dental caries prevalence among preschool children, caries levels increased with age and social inequalities persisted through the years, indicating a need of reviewing the policies to reduce the burden of this oral disease.