Lay summary
Community water fluoridation (CWF) is a cost-effective public health measure that aims to prevent tooth decay and reduce health inequities. In Aotearoa New Zealand, children, especially Māori and Pacific, experience high rates of dental decay and hospitalisations from preventable oral disease. However, CWF remains controversial due to concerns about possible effects on children’s neurodevelopment. Most, but not all, studies suggesting links between fluoride and neurodevelopmental outcomes involve exposure levels far above those used in CWF. Evidence at typical CWF levels (0.7–1.0mg/L) is limited, inconsistent, and methodologically weak. This project will use linked national datasets and a quasi-experimental study created by the phased rollout of CWF under the 2021 Fluoridation Act to evaluate both dental and neurodevelopmental outcomes. Results will provide robust, up-to-date evidence to inform health policy, address community concerns, and support equitable access to oral health care, particularly for Māori, Pacific and children living in deprived areas.