Fluoride intake has both beneficial effects – in reducing the incidence of dental caries – and negative effects – in causing tooth enamel and skeletal fluorosis following prolonged high exposure. The ranges of intakes producing these opposing effects are not far apart.
It is estimated that caries of the permanent teeth is the most prevalent of all conditions assessed, with 2.4 billion people globally suffering from caries of permanent teeth and 486 million children from caries of primary teeth. Public health actions are needed to provide sufficient fluoride intake in areas where this is lacking, so as to minimize tooth decay. This can be done through drinking-water fluoridation or, when this is not possible, through salt or milk fluoridation or use of dental care products containing fluoride, and by advocating a low-sugar diet.
Excessive fluoride intake usually occurs through the consumption of groundwater naturally rich in fluoride, particularly in warm climates where water consumption is greater, or where high-fluoride water is used in food preparation or irrigation of crops. Such exposure may lead to dental fluorosis or crippling skeletal fluorosis, which is associated with osteosclerosis, calcification of tendons and ligaments, and bone deformities. While the global prevalence of dental and skeletal fluorosis is not entirely clear, it is estimated that excessive fluoride concentrations in drinking-water have caused tens of millions of dental and skeletal fluorosis cases worldwide over a range of years. Although removal of excessive fluoride from drinking-water may be difficult and expensive, low-cost solutions that can be applied at a local level do exist.
WHO has published guidance to help communities control fluoride exposures to establish the important balance between caries prevention and protection against adverse effects. However, risk mitigation measures implemented should also take into consideration local contexts and sensitivities.