Early Childhood Caries and Its Associated Factors Among 5-Year-Old Children in Shenzhen City, China: A Cross-Sectional Study

<b>Background:</b> Early childhood caries (ECC) remains a critical public health challenge, yet recent prevalence data and risk factors are scarce in rapidly urbanizing regions like Shenzhen City, China. <b>Objectives</b>: This study aimed to assess ECC prevalence and identify risk factors among 5-year-old children in Shenzhen City. <b>Methods</b>: This cross-sectional survey was conducted in Shenzhen City in 2024, recruiting 5-year-old children through multistage sampling from kindergartens. Self-administered parental questionnaires were distributed to collect data such as demographic characteristics, socioeconomic background and oral health-related behaviors. One trained dentist conducted the oral examination in kindergartens using ball-ended community periodontal index probes and disposable dental mirrors with an intra-oral light-emitting diode light attached. Dental caries was assessed using diagnosis criteria recommended by World Health Organization. The decayed, missing, and filled primary teeth (dmft) were recorded. Zero-inflated negative binomial regression was applied to identify associations between risk factors and ECC. <b>Results</b>: Among 1462 participants (86% response rate), ECC prevalence was 58% (mean dmft: 2.5 ± 3.4), with untreated decay (dt) accounting for 92% of cases. Socioeconomic factors, including low family income (<i>p</i> < 0.001), non-local residency (<i>p</i> < 0.001), and low caregiver education level (<i>p</i> = 0.012), were significantly associated with higher dmft scores. Behavioral factors such as frequent sugary drink consumption (<i>p</i> = 0.005), lack of parental brushing assistance (<i>p</i> = 0.027), and non-fluoride toothpaste use (<i>p</i> = 0.008) also contributed to the risk of ECC. <b>Conclusions</b>: Over half of Shenzhen City's 5-year-olds suffered from ECC, predominantly untreated, driven by socioeconomic disparities and modifiable behavioral factors. Public health strategies must prioritize parental education, fluoride use and early preventive practices to reduce the burden of ECC.