The dental health benefits of adding fluoride to drinking water may be smaller now than before fluoride toothpaste became widely available, a review suggests.
Researchers from the universities of Manchester, Dundee and Aberdeen assessed evidence from 157 studies that compared communities that added fluoride to their water supply with communities that had no additional fluoride in their water.
Found the review that the benefit of fluoridation has declined since the 1970s, when fluoride toothpaste became more widely available.
Fluoride is known to reduce tooth decay. The addition of low levels of fluoride to drinking water has long been considered one of the greatest public health achievements of the last century.
“When interpreting the evidence, it’s important to think about the wider context and how society and health have changed over time,” says Anne-Marie Glenny, a professor of health science research at the University of Manchester and a co-author of the revised.
“Most of the studies on water fluoridation are more than 50 years old, before the availability of fluoride toothpaste. Contemporary studies give us a more relevant picture of what the benefits are now.”
Results of studies conducted after 1975 suggest that water fluoridation schemes may lead to slightly less tooth decay in children’s baby teeth.
Analysis of these studies, covering a total of 2,908 children in the UK and Australia, estimated that fluoridation could lead to an average of 0.24 fewer decayed baby teeth per child. However, the estimate comes with uncertainty, meaning it is possible that more recent schemes have no benefit, the researchers said.
By comparison, an analysis of studies with 5,708 children conducted in 1975 or earlier estimated that fluoridation reduced the number of decayed baby teeth by an average of 2.1 per child.
The Cochrane review could only draw conclusions about the impact on children’s teeth, with similar findings on baby and permanent teeth. There were no studies with adults that met the review’s criteria.
“The evidence suggests that water fluoridation may slightly reduce tooth decay in children,” said another co-author, Dr Lucy O’Malley, a senior lecturer in health services research at the University of Manchester.
“As the benefit has diminished over time, before a new fluoridation scheme is introduced, careful consideration must be given to cost, acceptability, feasibility and ongoing monitoring.”
Advocates have suggested that one of the main benefits of water fluoridation is that it reduces oral health disparities. The review tried to investigate this but did not find enough evidence to support the claim, although the researchers said this did not necessarily mean there was no effect.
“While water fluoridation may lead to small improvements in oral health, it does not address the underlying issues such as high sugar consumption and inadequate oral health behaviour,” says Janet Clarkson, a co-author and professor of clinical efficacy at the University of Dundee. “It is likely that any oral health preventive program should take a multi-level, multi-agency approach.”
In August, A US government report concluded that fluoride in drinking water at twice the recommended limit was linked to lower IQ in children.
The 324-page report did not reach a conclusion about the risks of lower levels of fluoride, saying more research is needed. It also did not answer what high levels of fluoride can do to adults.
