Table 1.

Fluoridation methods

	Water fluoridation	Milk fluoridation	Salt fluoridation
Foundation	First implemented in 1945 in USA (16).	Emerged in the early 1950s and was first investigated in Switzerland, the USA, and Japan (18).	Initiated in Switzerland in 1955 (17).
Supporting bodies	Recommended by the WHO (16).	Supported by the WHO and FAO (14).	Supported by community trials, WHO, FDI World Dental Federation recommendations and others (19).
Accessibility	More than 435 million people worldwide have access to either naturally or artificially fluoridated water (17).	More than one and a half million children worldwide currently consume fluoridated milk (24).	Presently, 300 million people worldwide use fluoridated salt (15).
Benefits	Substantially reduces the prevalence and incidence of dental caries in primary and permanent teeth (14).	Effective in caries prevention in primary and permanent teeth (22,23).	Inhibits dental caries (12); however, the effectiveness of fluoridated salt is uncertain since no randomized clinical trials were conducted to prove its efficacy (9).
Dosage	Fluoride concentration in natural water ranges from 0.01 to 100 ppm (13).	Daily dosage varies from 0.50 mg to 0.85 mg fluoride/child with children drinking around 200 mL of fluoridated milk/d for about 200 days per year (14).	Fluoride concentration ranges from 250~300 mg/kg of table salt (15).
Feasibility	Less than 10% of the world’s population is able to have access to fluoridated water (10).	It is a simple process and the cost of fluoridated milk is usually the same as non-fluoridated milk (25).	During operation, the estimated cost is 10 to 100 times lower than that associated with water fluoridation programs (17).
Efficiency	Considered more efficient than milk fluoridation (14).	Fluoride added to milk forms insoluble complexes that make fluoride absorption difficult and less efficient compared with water fluoridation (14).	In some circumstances salt fluoridation was a more cost-effective caries preventive for children than either fluoridated items such as water, milk or mouth rinses (15).
Health Considerations	To minimize fluoride toxicity, the fluoride concentration in drinking water in the US has been controlled with a recommended level of 0.8~1.0 ppm (13).	It is suggested that children begin to drink fluoridated milk preferably before the age of 4 years (24).	In order to achieve a meaningful effect on caries control, the minimal acceptable level of fluoride is attained at a concentration of 200 mg/kg (17). No side effects or significantly mottled enamel were shown in groups using salt containing 200, 250, or 350 mg of fluoride/kg in comparison with groups not consuming fluoridated salt (10). A contraindication of promoting salt fluoridation may be due to the risk of hypertension linked to high salt consumption. The upper tolerable limit for fluoride intake has been estimated to be 0.12 mg/kg/d, which is equivalent to about 5 mg/d for 9 to 14-year-old children and 7 mg/d for 15-year-old and older people, including pregnant and lactating women (17). No adverse impact has been identified when combining iodide and fluoride in salt (17).

WHO, World Health Organization; FAO, Food and Agriculture Organization; FDI, Fédération Dentaire Internationale.