Water fluoridation for the prevention of dental caries.

Systematic review and meta-analysis of mostly observational community studies, largely school-based, conducted across multiple countries. The main caries evidence involved children aged 3 to 16 years; some studies also assessed dental fluorosis and a small number addressed cessation or socioeconomic differences.

Community water fluoridation (artificial or natural) was evaluated against non-fluoridated water. Included studies commonly used fluoride concentrations around 0.8 to 1.2 ppm, with non-fluoridated water defined as 0.4 ppm or less; some fluorosis studies examined higher concentrations up to 2 to 4 ppm or more.

Water fluoridation was associated with less dental caries in children, but the evidence is low quality and mostly comes from studies published before 1975. Pooled estimates showed reductions in dmft of 1.81 (95% CI 1.31 to 2.31; 9 studies) and in DMFT of 1.16 (95% CI 0.72 to 1.61; 10 studies), with absolute increases in caries-free proportions of 0.15 for deciduous dentition and 0.14 for permanent dentition. Higher fluoride exposure was associated with more dental fluorosis: aesthetic-concern fluorosis at 0.7 ppm was 12% (95% CI 8% to 17%; 40 studies, 59,630 participants), and any-level fluorosis was 40% (95% CI 35% to 44%; 90 studies, 180,530 participants). The review concluded that contemporary, well-controlled research is needed because applicability to current populations and lifestyles is uncertain.

Evidence was largely observational, with high risk of bias, heterogeneity, and limited applicability to modern settings. Most studies were conducted before 1975, and there was insufficient evidence for adults, cessation effects, or socioeconomic disparities in caries. Fluorosis estimates were also affected by bias and between-study variation.