Early childhood caries at its start: oral health disparities in Thai toddlers.

Despite a declining trend, early childhood caries (ECC) remains a public health concern, particularly among very young children. In Thailand, ECC prevalence is consistently higher in provincial areas than in the capital city and remains underexplored. This study examined disparities in oral health status among infants and toddlers living in the capital and provincial areas, as well as differences in parental sociodemographic and economic status (SDES), oral health knowledge (OHK), and oral health behaviours (OHB), and identified key factors associated with ECC among Thai children aged 6-36 months. This cross-sectional study included 263 parents of children aged 6-36 months attending a university hospital in Bangkok and two provincial hospitals. Parents completed validated questionnaires assessing SDES, OHK, and OHB. Children underwent oral examinations for caries using the ICDAS scoring system and oral hygiene assessment via the Debris Index-Simplified. Statistical analyses included chi-square, Mann-Whitney U, and regression models to identify factors associated with oral health outcomes. The overall caries prevalence was 39.5%. Children residing in provincial cities exhibited significantly poorer oral hygiene (median [IQR]: 1.50 [1.33] vs. 0.67 [1.16]) and more severe dental caries than those in the capital city (30.6% vs. 9.7% of total tooth surfaces). Parents in the capital city demonstrated significantly higher OHK scores than those in provincial areas (median [IQR]: 8.0 [2.0] vs. 5.0 [4.0]), and unfavourable OHBs were more common among provincial families. Multivariable binary logistic regression analysis identified provincial residence, a greater number of erupted teeth, cariogenic snacking, and sugar-sweetened beverage (SSB) consumption as significant factors associated with both poor oral hygiene and ECC, while lower parental education level was associated with poor oral hygiene only. Significant disparities in SDES, parental OHK, and OHBs were observed between capital and provincial residents, with children in provincial areas exhibiting poorer oral hygiene and a higher prevalence of ECC. Key associated factors for poor oral hygiene and ECC included provincial residence, parental education lower than a bachelor's degree, increased number of erupted teeth, and early consumption of cariogenic snacks and SSBs.