Water fluoridation provides a modest benefit for children’s teeth in an era of fluoride toothpastes, but does not shrink inequalities in dental health between rich and poor communities, research has revealed.
Fluoride, a naturally occurring mineral, has been added to drinking water for decades in areas where natural levels are low in a bid to tackle tooth decay.
Water fluoridation occurs in about 25 countries, according to the UK government, and encompasses about 6 million people in England, largely in the West Midlands and the north-east.
Among areas currently looking at introducing the approach are County Durham, Sunderland, South Tyneside and Teesside.
But while water fluoridation is supported by all of the UK chief medical officers, it has proved controversial. What’s more, many studies examining the impact of water fluoridation were conducted before fluoride toothpaste became a household staple.
Now researchers say that while water fluoridation appears to bring benefits, these are much smaller than earlier research suggested.
“We’re aware of a number of different areas that are looking at implementing water fluoridation, so it’s very much a live issue at the moment,” said Dr Michaela Goodwin, senior investigator on the Catfish study, from the University of Manchester.
The team, which published its findings in the journal Public Health Research, focused on two areas of Cumbria, one without water fluoridation and one where fluoridation had only recently restarted.
In both areas they recruited children aged around five years old when fluoridation restarted in parts of the county in 2013, and hence had not previously been exposed to fluoridated water – as well as babies who were conceived after this point in time.
Experts examined the milk teeth of the younger group at three and five years of age, and newly erupting adult teeth for the older group at ages five, seven and 11 years old.
The results from 1,444 children in the younger cohort reveal that 17.4% of those living in fluoridated areas had decayed milk teeth, compared with 21.4% for those in areas without water fluoridation.
After taking into account factors such as age, sex and deprivation, the team found the odds of decay for those in the water fluoridation group compared with the no fluoridation group were 26% lower.
There was no clear evidence of an effect for the 1,192 older children. While the team say this may suggest an important role for fluoride exposure in the womb, they add it could be that not enough time had passed for cavities to develop in the adult teeth.
The team added that the number of teeth that were decayed, missing or filled was lower in fluoridated areas for both younger and older children, suggesting lower rates of decay.
The researchers say further analysis suggests water fluoridation is cost effective – although this did not take into account any organisational costs.
However the study found no evidence that water fluoridation shrinks inequalities in dental health between wealthier and more deprived communities, suggesting other measures should also be considered. The team also say the younger group should be assessed at age 11 for fluorosis – a condition where teeth become discoloured.
Prof Mike Kelly, a senior member of the research team from the University of Cambridge, said the new data will help those weighing up whether to add fluoride to water. “They can now make that decision on the basis of the most up-to-date information, not on data that’s 40 years old,” he said.
Eddie Crouch, chair of the British Dental Association, said ministers need to act to prevent tooth decay.
“From water fluoridation to supervised brushing in schools, they have tried and tested policies to hand that can save money and improve oral health,” he said. “All that’s missing is the will to implement them.”