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Optimal Fluoride Concentration in Drinking Water for Preventing Dental Fluorosis and Caries in 8-12-Year-Old Children in Qingdao, China: A Restricted Cubic Spline and Spatial Epidemiological Analysis Following Rural Safe Drinking Water Interventions in Endemic Fluorosis Region.
| Biological Trace Element Research | Dou X, Liu X, Liu S, Ge C, Yan S, Wu D, Meng X, Li X, Pei J, Ji F. |
Caries Children China Dental Fluorosis Human Study

Abstract

Maintaining optimal fluoride levels in drinking water is crucial for balancing dental caries prevention and fluorosis risk in children. This cross-sectional study investigated 12,163 children aged 8–12 years across 934 villages in Qingdao, China, following water safety interventions in an endemic fluorosis regions. Water fluoride concentrations were measured via spectrophotometry, while dental examinations assessed fluorosis (Dean’s classification) and caries (DMFT index). Spatial epidemiological mapping, restricted cubic spline (RCS) models, and multivariate logistic regression were integrated to analyze geographic patterns, dose–response relationships, and risk thresholds. Results demonstrated an overall fluorosis prevalence of 3.2% and caries prevalence of 27.0%. RCS analysis revealed a nonlinear positive association between fluoride levels and fluorosis risk (threshold: 0.70 mg/L), alongside a U-shaped caries–fluoride relationship exhibiting minimal caries risk at 0.70–0.73 mg/L. Multivariate regression identified significantly elevated fluorosis odds (adjusted OR?=?1.71, 95%CI 1.29 – 2.28) at concentrations?>?0.85 mg/L, while 0.70–0.73 mg/L optimally minimized caries. Spatial clustering of high-fluoride regions in northwestern Qingdao correlated with fluorosis hotspots. These findings establish 0.70–0.73 mg/L as the optimal fluoride concentration range for dual caries prevention and fluorosis mitigation in this population. The study advocates for dynamic adjustments to water fluoridation standards and geographically targeted interventions in high-risk regions, offering evidence-based strategies for public health policymaking in fluorosis-endemic regions.

Data Availability

No datasets were generated or analysed during the current study.

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Funding

This research was funded by the National Natural Science Foundation of China (82473747 and 82273749).

Author information

Authors and Affiliations

  1. Qingdao Municipal Center for Disease Control and Prevention, Qingdao, 266000, Shandong Province, China

    Xiaojuan Dou, Xiaoyi Liu, Changxun Ge & Fengying Ji

  2. Pingdu City Center for Disease Control and Prevention, Pingdu, 266700, Shandong Province, China

    Shitao Liu

  3. Key Lab of Etiology and Epidemiology, Education Bureau of Heilongjiang Province & Ministry of Health (23618504), Center for Endemic Disease Control, Chinese Center for Disease Control and Prevention, Harbin Medical University, Harbin, Heilongjiang Province, 150081, China

    Shirui Yan, Di Wu, Xinxiao Li & Junrui Pei

  4. Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University, Chongqing, China

    Xinyue Meng

  5. Public Health College, Qiqihar Medical University, Qiqihar, Heilongjiang, China

    Junrui Pei

Contributions

Concept and design: Fengying Ji and Junrui Pei. Acquisition, analysis, or interpretation of data: Xiaojuan Dou, Xiaoyi Liu, Shitao Liu, Changxun Ge, Shirui Yan, Di Wu, Xinyue Meng, Xinxiao Li, Junrui Pei. Drafting of the manuscript: Fengying Ji, Junrui Pei, Xiaojuan Dou, Xiaoyi Liu, Shirui Yan, Di Wu. Critical review of the manuscript for important intellectual content: Fengying Ji, Junrui Pei, Shirui Yan, Di Wu. Statistical analysis:Shirui Yan, Di Wu, Xinyue Meng, Xinxiao Li. Obtained funding:Fengying Ji. Administrative, technical, or material support:Xiaojun Dou, Xiaoyi Liu, Shitao Liu, Changxun Ge, Fengying Ji. Supervision:Fengying Ji and Junrui Pei.

Corresponding authors

Correspondence to Junrui Pei or Fengying Ji.

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Competing interest

The authors declare no competing interests.

Supplementary Information

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ABSTRACT ONLINE AT https://link.springer.com/article/10.1007/s12011-025-04768-x