The fluoride debate – what do the experts say?

The impending High Court decision on the legality of fluoridation in Taranaki, and Paul Connett’s current speaking tour in New Zealand is bringing the fluoridation issue into the news again. New Zealand’s Science Media Centre (SMC) responded by conducting a Q&A with public health experts on fluoride. Here are the results.

Professor Barry Borman

Associate Director, Centre for Public Health Research, Massey University (with Ms Caroline Fyfe), responds:

Given the body of scientific evidence available, are you convinced that water fluoridation is an effective public health intervention?

“The overwhelming evidence from the peer-reviewed literature is that community water fluoridation is a highly effective and cost effective public health method for improving the oral health status of a population.”

What are the main benefits of fluoridation in New Zealand?

“Improving the oral health of the population, especially among those populations which have a poor oral health status, for example those on low incomes.”

What is at stake if more communities choose to end the practice?

“Depriving their local population of a cost effective method for improving (and/or maintaining) the oral health.”

Why do you think water fluoridation continues to be such a heatedly debated issue?

“Primarily because of the engrained views held by both the anti-fluoridation and pro-fluoridation groups, together with a lack of understanding and appropriate interpretation of the literature and nuances involved in the many studies. In many instances, results from the literature are used to support a view, but many of the studies have used poor study design, lack validity, and have varying degrees of bias. It is the validity of the study design that is critically important and not just the focus on the results.

“For example, a number of studies have been carried out in areas where the naturally occurring high levels of fluoride (eg, China and India) are well in excess of those used for community water fluoridation in New Zealand. Some studies adjust for the potential effects of all sources of fluoride, while others don’t, while some make an adjustment for differences between study and control population, while others don’t. The results from a recent meta-analysis showing a relationship between water fluoridation and children’s IQ have been widely used to support the position of the anti-fluoridation lobby, However, the study results have been shown to be flawed in a number of aspects (Borman B, Fyfe C. Fluoride and children’s IQ, NZ Med J, 2013).

“Much of the current confusion over community water fluoridation can also be attributed to the poor communication of the science by scientists.”

What should public health officials be doing to more effectively engage the public on this issue?

“Develop a greater understanding of the principles and techniques of risk communication and how a population perceives a risk to their health. The old adage remains: the things that scare people are not necessarily the things that kill or harm them.”

Professor Murray Thomson

Professor of Dental Epidemiology and Public Health, University of Otago, responds:

Given the body of scientific evidence available, are you convinced that water fluoridation is an effective public health intervention?

“Yes. It is important to remember that community water fluoridation is not a “magic bullet”, though; it will not eliminate tooth decay, but it will reduce it. How? Tooth decay begins as very small “etchings” of the dental enamel; these occur as dietary sugars are fermented (turned into weak acids) by bacteria within the plaque biofilm which forms on the tooth surface.

“Once those sugars have been used up, that demineralisation can be counterbalanced with subsequent remineralisation by calcium and phosphate ions from the saliva, slowly replacing the minerals which were lost. There is a continual cycling between demineralisation and remineralisation; the longer spent in the former, the greater the chance of a cavity. If fluoride is present, it not only enters the enamel, making it more resistant to acid attack, but it also inhibits demineralisation and the plaque bacteria.

“NZ evidence of fluoridation’s effectiveness has come from a number of studies which have shown that not only is decay experience lower among children living with community water fluoridation, but socio-economic inequalities are also lower. Data from our most recent national oral health survey provide evidence for a considerable effect in adults as well – and this effect is becoming more important as more and more Kiwis retain their teeth into old age. The benefits are there for Kiwis of all ages.”

What are the main benefits of fluoridation in New Zealand?

“Lower dental caries rates among children and adults alike. Fewer small children having to have teeth removed in hospital under a general anaesthetic. In area without community water fluoridation, children who do have to have that done present with more decay and at a younger age. Systematic reviews of the international evidence show that adults drinking fluoridated water have 27% less tooth decay experience. Given that the average middle-aged NZ adult has had 18 decayed, missing or filled teeth, that’s a difference of 4 teeth affected, on average.”

What is at stake if more communities choose to end the practice?

“There will be much more tooth decay, and that will have its greatest impact among people living in socio-economically deprived areas, as well as among Maori and Pacifika. It won’t happen overnight, of course, given the chronic, cumulative nature of the disease, but it will definitely get worse. Those who are opposed to community water fluoridation assert that we don’t need it: they argue that people can take fluoride tablets, brush with fluoride toothpaste and use mouthrinses if they want to use fluoride to prevent decay.”

“That’s all very well for the ‘worried well’ in the middle classes (who tend to have more positive self-care and health behaviours anyway), but it is neither feasible nor humane to leave the rest of the population to it. For example, we know from the 2009 national dental survey that only 59% of adults in the most deprived 20% of neighbourhoods brush their teeth twice daily with fluoride toothpaste. There is therefore a role for the State in preventing tooth decay in the NZ population: community water fluoridation remains the most efficient, effective and rational way to do it.”

Why do you think water fluoridation continues to be such a heatedly debated issue?

“There is a small but very vocal minority who have an anti-science, anti-public health agenda. They are very good at targeting the local body politicians who have to make the decision on whether to fluoridate or not. Being single-issue zealots, they have plenty of time and energy to do so. They are also funded well enough to bring overseas rhetoricians/polemicists into NZ periodically on speaking tours.”

What should public health officials be doing to more effectively engage the public on this issue?

“That’s a good question. The doggedness and sheer persistence of the anti-fluoride lobby means that public health officials could easily spend all of their time on the issue, but they actually have a plethora of more pressing, relevant public health issues to deal with, such as dental caries, tobacco, our alarming and rising obesity rates, and so on.” 

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If you would like to contact a New Zealand expert about fluoride, please contact the SMC (04 499 5476; smc@sciencemediacentre.co.nz).

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