Fluoridation and the risk of multiple amalgam or composite resin restorations for privately insured Massachusetts children: A retrospective cohort study.

BACKGROUND: Community water fluoridation (CWF) is widely associated with reduced childhood caries. The authors examined whether CWF reduces amalgam or composite resin restoration risk among privately insured children in Massachusetts. METHODS: In this retrospective cohort study, the authors analyzed dental insurance claims (2016-2019) linked to municipal fluoridation and Internal Revenue Service data among 35,610 privately insured children aged 1 through 16 years. Linear regression estimated adjusted mean differences in amalgam or composite resin restorations to examinations ratios and Poisson regression with log-link estimated adjusted risk ratios for multiple amalgam or composite resin restorations. Age stratification included teenagers entering the study (n = 9,215). Models adjusted for age, sex, income, topical fluoride, and sealants. RESULTS: In adjusted models, the CWF cohort had a lower amalgam or composite resin restorations to examinations ratio (-0.034; 95% CI, -0.057 to -0.011; P = .004). A lower ratio was observed among adolescents 13 years and older at study entry (-0.092; 95% CI, -0.155 to -0.030; P = .004). Results of secondary threshold analyses showed generally larger relative risk reductions with higher treatment thresholds reaching an overall 19.0% reduced risk for more than 8 amalgam or composite resin restorations (estimate, -0.211; 95% CI, -0.360 to -0.062; P = .005). Similarly, a 26.9% reduced risk was observed for more than 7 amalgam or composite resin restorations among adolescents 13 years and older at study entry (estimate, -0.312; 95% CI, -0.511 to -0.115; P = .002). CONCLUSIONS: The results of this study showed that privately insured children exposed to CWF had a lower risk of undergoing restorative dental treatment, with greater protection generally observed at higher treatment counts. These findings support the extension of CWF's preventive public health benefits to privately insured children. PRACTICAL IMPLICATIONS: Results showed CWF remains relevant for reducing dental treatment needs and may inform municipal fluoridation decisions.