Two new studies in this week's British Medical Journal illustrate the positive and negative aspects of adding fluoride to public water supplies as a way to reduce tooth decay.
One study suggests that longterm exposure to fluoridation may significantly reduce the risk of hip fractures in women aged 65 or older. The other indicates that while fluoridation helps to reduce tooth decay by about 15 per cent, it increases mottled discolouration of the teeth, a condition known as fluorosis.
The study of bone mineral density and fractures was carried out by Oregon Health Sciences University. Its results run counter to claims of increased fracture incidence made in earlier papers.
The bone density and fracture rates in a group of 9,000 women 65 or older was studied, including 2,563 women with no exposure to fluoridated water over 20 years and 3,218 women with continuous exposure.
Those who had fluoridated water had higher bone mineral density at the hip and at the lower spine and a 31 per cent reduced risk of hip fracture and 27 per cent reduced risk of vertebral fracture than women with no exposure. Those who had fluoridated water only some of the time had a fracture incidence similar to women with no exposure.
The second paper, a review of more than 200 studies on the health effects of water fluoridation, was prepared by the National Health Service Centre for Reviews and Dissemination at the University of York. The authors showed that fluoridation represented a trade-off with lower levels of decay matched by increased fluorosis.
The researchers suggested that many of the studies were of a poor quality but found a median 15 per cent reduction in tooth decay. This on average meant 2.25 fewer decayed, missing and filled teeth among children living in fluoridated areas compared to non-fluoridated areas.
