New US data have shown that overexposure to fluoride has led to an increase in fluorosis (mottled tooth enamel).
The researchers analysed data on fluorosis from the National Institute of Dental Research's (NIDR) survey of dental caries in school children (1986-87) as well as data from the 1930s, looking for changes in the incidence of fluorosis.
The highest incidences of fluorosis were where water was naturally fluoridated or where fluoride had been added. The lowest incidence was in areas where water was not fluoridated.
However, say the researchers, water may not be the biggest problem. Fluoride overexposure is aggravated by other sources, including those not intended to be ingested, like toothpaste.
This fact may explain the finding that the largest increase in the incidence of fluorosis was among children living in areas where the water is not fluoridated (J Am Dental Assoc, 2002; 133: 157-65).