Investigation 006
The Fluoride Decision
A quarter of a tooth, and everything it was traded for
Environment & exposure
Fluoride
The most-swallowed drug never prescribed: added to water at 0.7 mg/L, and the contemporary caries benefit measures about a quarter of a tooth.
What we are reading
Gathered for the investigation and not yet written up. Each note says what the paper does and does not show.
- Iheozor-Ejiofor Z, Walsh T, Lewis SR, Riley P, Boyers D, Clarkson JE, Worthington HV, Glenny AM, O'Malley L. Water fluoridation for the prevention of dental caries.10.1002/14651858.CD010856.pub3 · PMID 39362658
THE central document and the one almost nobody quotes accurately. 157 studies, ALL non-randomised, every one downgraded for risk of bias. Contemporary evidence (post-1975, i.e. after fluoride toothpaste became universal): starting fluoridation changes dmft by 0.24 teeth (95% CI -0.03 to 0.52) — roughly a QUARTER OF ONE TOOTH, low certainty, and the confidence interval includes no benefit at all. Caries-free children: 4 percentage points (primary), 3 points (permanent), both CIs crossing zero. Cessation: very low certainty, cannot say. No eligible study reports caries outcomes in ADULTS at all. Harms, from the 2015 arm: at 0.7 ppm about 12% have fluorosis of aesthetic concern (95% CI 8-17%, 40 studies, 59,630 people) and about 40% have fluorosis of any level (90 studies, 180,530 people). That is the honest trade — a quarter of a tooth against a two-in-five chance of marking the enamel.
- Yeh CH, Wang YL, Vo TTT, Lee YC, Lee IT. Fluoride in Dental Caries Prevention and Treatment: Mechanisms, Clinical Evidence, and Public Health Perspectives.10.3390/healthcare13172246 · PMID 40941599
A pro-fluoride narrative review, useful precisely because it concedes the shape of the problem: study heterogeneity, protocol variation, fluorosis, and 'possible neurodevelopmental effects' named as persistent uncertainties. Also the cleanest statement that emerging alternatives — nano-hydroxyapatite, bioactive glass, probiotics — are 'promising but currently supported by limited clinical data'.
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