Water fluoridation

Water fluoridation is the controlled addition of fluoride to public water supplies to reduce tooth decay. Fluoridated water maintains fluoride levels effective for cavity prevention, achieved naturally or through supplementation.^[2] In the mouth, fluoride slows tooth enamel demineralization and enhances remineralization in early-stage cavities.^[3] Defluoridation is necessary when natural fluoride exceeds recommended limits.^[4] The World Health Organization (WHO) recommends fluoride levels of 0.5–1.5 mg/L, depending on climate and other factors.^[5] In the U.S., the recommended level has been 0.7 mg/L since 2015, lowered from 1.2 mg/L.^[6][7] Bottled water often has unknown fluoride levels.^[8]

Tooth decay affects 60–90% of schoolchildren worldwide.^[9] Fluoridation reduces cavities in children, with Cochrane reviews estimating reductions of 35% in baby teeth and 26% in permanent teeth when no other fluoride sources are available, though efficacy in adults is less clear.^{[10][needs update]} In Europe and other regions, declining decay rates are attributed to topical fluorides and alternatives like salt fluoridation and nano-hydroxyapatite.^{[3][11][12][13]}

Fluoridation began in the U.S. and now covers 72% of the population as of 2022.^[14][15] Globally, 5.4% of people receive fluoridated water, though its use remains rare in Europe, except in Ireland and parts of Spain.^[16] The WHO, FDI World Dental Federation, and Centers for Disease Control and Prevention endorse fluoridation as safe and effective at recommended levels.^[17][18] Critics question its risks, efficacy, and ethical implications.^[19][20][21]

Recent systematic reviews suggest an association between higher fluoride exposure and lower IQ in children.^[22][23][24] These findings remain debated among experts and public health organizations.^{[25][26][27][28]}