Social inequalities in dental caries by municipal oral healthcare coverage

OBJECTIVE: To assess whether socioeconomic inequalities in childhood dental caries vary across different trajectories of municipal oral healthcare coverage. METHODS: This cross-sectional study linked data from 7185 5-year-old children in the 2023 Brazilian National Oral Health Survey to monthly municipal oral healthcare coverage data from January 2019 to December 2021. Four coverage trajectories were identified using group-based trajectory modelling: always low, medium-low, medium-high, and always high. Dental caries was assessed using the dmft and pufa indices. Income-related inequalities were measured using the Slope and Relative Index of Inequality (SII and RII), adjusted for child demographic characteristics and geographical factors. RESULTS: For dmft, no interaction between municipal oral healthcare coverage and either the SII (p = 0.064) or the RII (p=0.257) was found, indicating that income-related inequalities in dmft did not differ across coverage trajectories. For pufa, interactions were observed between municipal oral healthcare coverage and both the SII (p = 0.032) and the RII (p = 0.025). Although absolute and relative income-related inequalities in pufa were evident across all coverage trajectories, they were more pronounced in municipalities with medium-high coverage than in those with always-low coverage. CONCLUSIONS: This study found little evidence that socioeconomic inequalities in childhood dental caries differed across municipalities with varying levels of oral healthcare coverage. CLINICAL SIGNIFICANCE: Expanding oral healthcare coverage alone may not eliminate socioeconomic inequalities in oral health among young children, as these inequalities are rooted in broader social and structural determinants that extend beyond access to healthcare services.