Fluoride Debate: Why I support fluoridation – response to Connett

This is Ken Perrott’s response to Paul Connett’s first criticisms of Ken’s article Fluoride debate: Why I support fluoridation – Response from Connett.

For Ken Perrott’s original article see – Fluoride debate: Why I support fluoridation.

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First this issue of science and citations? Yes, my last article was general and concentrated on the philosophy of science and social aspects – both of which are important to me and central to why I support fluoridation.  But Paul seems not to have appreciated or understood my first section on scientific aspects so I will develop part of that, the nature of fluorine in apatites, further here. I will throw in a few citations just to keep Paul and my other critics happy (more on the use of citations later).

Apatites contain structural fluoride

I briefly referred to the nature of apatites and the occurrence of fluoride as a natural constituent. Paul seems not to get this as he again refers to fluoride as something external, and not a natural, normal, part of apatites. He is mistaken in his belief that I claim “that fluoride is needed to react with our bio-apatites and make them stronger, less soluble and in the case of teeth less vulnerable to tooth decay.” (My stress).

I don’t claim that at all. I argue that apatites, including bioapatites, are not pure end members such as hydroxylapatite, but naturally (and normally) contain species like F and carbonate as part of their structure. isomorphous substitution of these species for phosphate and oxygen occur during formation of the apatite compounds. This isomorphous substitution of F for O strengthens the apatite and lowers it’s solubility compared with the hydroxylapatite end member. Carbonate substitution for phosphate can have an opposite effect – things are never simple so there is a balancing act which makes isomorphous substitution of fluoride even more important. The bioapatites in our body contain both F and carbonate as normal, natural components (see figure below). The  incorporation of ions like fluoride into bioapatites can change their solubility product by several orders of magnitude according to Driessens (1973). Planer at al (1975) attributes the improved stability of bone to “the isomorphous substitution of fluoride in the apatite structure.”

(None of this denies the the negative effects of excessive fluoride intake on our bones and teeth).

This is why Wopemka and Pasteris (2005) argue “the apatite phase in bone should not be called hydroxylapatite.” This is also the reason why there are “limitations to the use of the stoichiometric mineral hydroxylapatite as a mineral model for the inorganic phase in bone.” I second this and find unfortunate the simplification we often see in more general texts where bioapatites are discussed as if they were the end members hydroxylapatite or fluorapatite rather than an intermediate hydroxyl-carbonate-fluoroapatite of somewhat variable composition.

The fluoride we ingest is involved in the formation of bioapatites right from the beginning. This is why we see increased risks of weakened bones and teeth when dietary fluoride intake is insufficient. It can also be lost from actively growing bones and other bioapatites when fluoride intake is reduced. See Kurland et al (2007) for an example of the reverse of fluorosis (probably caused by surreptitious ingestion of toothpaste) once fluoride inputs had been reduced.

Understanding the complex nature of bioapatites and the effect of composition on structure and strength is important to appreciating the role of ingested fluoride on producing healthy bones and teeth. Unfortunately this aspect is often neglected, or purposely overlooked or hidden, when attention is concentrated on the mechanism of surface reactions of fluoride with existing teeth in inhibiting tooth decay.

However, some researchers are stressing that the beneficial effect of fluoride arises from effects of ingested, or systemic, fluoride on pre-eruptive teeth as well as surface reactions on existing teeth. Newbrun (2004), for example, stressed in a review of the systemic role of fluoride and fluoridation on oral health:

“The role of systemic fluoride in caries prevention is neither “minimal” nor “of borderline significance.” On the contrary, it is a major factor in preventing pit and fissure caries, the most common site of tooth decay. Maximal caries-preventive effects of water fluoridation are achieved by exposure to optimal fluoride levels both pre- and posteruptively.”

I will now discuss those surface reactions.

Topical confusion once again

Having dealt with this issue twice now (admittedly only briefly) I am surprised Paul could interpret my understanding of the beneficial role of fluoride on teeth as requiring:

“the need to put fluoride in the drinking water so after passing through the whole body it ends up in our saliva and that this is the delivery system which reduces tooth decay.”

I have never claimed that at all. Still, local anti-fluoride activists accuse me of this despite my many specific refutations. Paul’s characterisation of the “topical mechanism” is common among such activists and, as I said in a previous article, an example of a bait and switch fallacy.

Earlier this year I wrote about the so-called “topical” mechanism and the way it was being misrepresented by anti-fluoride activists in two articles – Fluoridation – topical confusion and Topical confusion persists. I will just repeat myself a bit here to clarify.

The US Center for Disease Control describes this “topical” or surface mechanism in its  report Recommendations for Using Fluoride to Prevent and Control Dental Caries in the United States:

” . . drinking fluoridated water, brushing with fluoride toothpaste, or using other fluoride  dental products can raise the concentration of fluoride in saliva present in the mouth 100-to 1,000-fold. The concentration returns to previous levels within 1–2 hours but, during this time, saliva serves as an important source of fluoride for concentration in plaque and for tooth remineralization.”

So let us be clear, they are referring (in the case of fluoridated water) to fluoride ions transferring from the water (or food) to saliva (and biofilms on the teeth). There is no assumption that the salivary fluoride must come only from ingested fluoride after “passing through the whole body.” The latter, of course happens, but contributes a smaller amount. There are literature reports that this lower concentration can also contribute to the “topical” mechanism – but I am not myself advocating that as necessary.

The diagram below portrays this – the fluoride is going directly from the drink and food into the saliva:

Tooth decay occurs because when the pH at the tooth surface is lowered (this happens when bacteria decompose sugars and other carbohydrates) some of the calcium and phosphate in the bioapatite at the tooth surface dissolves – mineralisation. With time the pH increases and the reaction is reversed – calcium and phosphate ions at the tooth surface reform as a solid hydroxylapatite surface phase (remineralisation). The acidity (or pH) is an important factor in the dissolution and prtecipitation fo apatites.

When fluoride is present at the tooth surface a fluorohydroxyapatite is formed in the surface phase. This is “harder” – it doesn’t dissolve as readily. Consequently the incorporation of fluoride into the tooth surface reduces mineralisation – and enhances remineralisation. It inhibits tooth decay.

Fluoride in fluoridated water and food does this very effectively. Because we drink and eat often, dietary forms of fluoride help to maintain a useful concentration of saliva fluoride over time.

Topical application methods (toothpastes and dentrifices) are a supplement to fluoridated water and dietary fluoride, but not a substitute – partly because they are not applied as often (if at all). However, dentrifices and dentist’s fluoride treatments may cause formation of CaF₂ globules on the tooth surface (because of the high F concentration) which then slowly release their F over time to maintain saliva concentrations at an appropriate level (see the  review article Mechanisms of Action of Fluoride for Caries Control by Buzalaf, Pessan, Honório, and ten Cate JM (2011)).

The “topical” or surface mechanism which operates with fluoridated water is effective because it is regular (much more regular that topical application methods) and this helps maintain fluoride concentrations in saliva and tooth biofilms are effective levels.

Incidentally, this is also a reason water fluoridation is an effective social health policy.  It means that the whole population can and does access the “topical mechanism” without thinking about it (as is required with toothpaste, mouth rinse and dentist fluoride treatments).

In summary, science supports both a systemic and a surface (“topical”) role for the beneficial effects of fluoridated water.

Benefits for bones

Paul asks for “scientific evidence that interaction [of fluroide] with the bones is beneficial.” As I described above that question actually misrepresents the situation. It is not the interaction with bones that is important but incorporation into bones during their formation and growth. Fluoride does not have to “react with our bioapatites,” as Paul puts it. The fluoride is a component of the bioapatites – See first figure above.

There are numbers of scientific papers that can be cited to show a beneficial role for fluoride in bones. I will just refer here to  Li et al (2001) (full text here) because it does offer a useful graphic demonstration of that beneficial effect – in this case of the overall incidence of bone fractures. Figure 2 from this paper shows that the incidence of fractures is lowest at concentrations similar to that used for water fluoridation, with increased incidence at both lower and higher concentrations.

Incidentally, one of our commenters Kurt Ferre draws attention to the fact Paul Connett is aware of this paper – at least he referred to it in his 50 reasons to oppose fluoridation where Paul notes:

” One very important study in China, which examined hip fractures in six Chinese villages, found what appears to be a dose-related increase in hip fracture as the concentration of fluoride rose from 1 ppm to 8 ppm (Li 2001) offering little comfort to those who drink a lot of fluoridated water. “

Actually the study did not show what Paul claims –  “a dose-related increase in hip fracture as the concentration of fluoride rose from 1 ppm to 8 ppm.” The particular data relates to overall fractures, and not hip fractures. And rather than demonstrating “a dose-related increase” it just shows a significant increase  in the 4.32 – 7.97 ppm group when compared with the 1.00 a 1.06 ppm group.

But really he should have mentioned the significant increased incidence of fractures in the 0.25 – 0.34 ppm group (to the same incidence as at 8 ppm) as this is consistent with a beneficial role for fluoride at around 1 ppm.  It demonstrates the negative effects of deficient intake of fluoride.

This brings us to the next issue – the selective approach to scientific literature and use of citations.

Approaching the literature – purposely or objectively

One thing that sticks out like a sore thumb when Paul and other opponents of fluoridation cite research papers is the predominance of studies from China and India. And the journal Fluoride, which is not considered a high quality journal by the scientific community, is often cited.

Just on the possibility of chance we might expect a better representation of countries of origin of the research, and of journals. I believe this demonstrates a selective approach to the literature.

If you wish to promote a pet theory or way-out idea it is possible to find a “scientific” citation to support it. All you need is Google and a fair bit of confirmation bias. The latter is a normal problem for all of us – if we have a stong committment to an idea we can usually find some handy citations to support it (and ignore those that don’t). On top of that we can interpret those papers (or more likely just their titles or abstracts – who bothers to read the full text?) to fit in with our ideas.

It is just so easy to make any argument look “sciency” using citations these days. And who bothers checking them? A good proportion of readers seem to be convinced just by the presence of citations. (Or unimpressed by the lack of them – Paul described my last article as “very, very short on science”  because “surprisingly you gave no scientific citations at all.”)

So citations do get thrown around a lot in this discussion – often in a meaningless and thoughtless way. As for their interpretation – in my articles Fluoridation – are we dumping toxic metals into our water supplies? and Fluoridation – it does reduce tooth decay I give examples from the local anti-fluoride activist web site FANNZ where cited sources are claimed to say the opposite of what they do say! (It always pays to check citations from ideologically motivated sources like this – I certainly do now).

Fortunately working scientists usually have the discipline of peer review and continual critique of their findings and idea by their scientific community. This encourages an ethos of objectivity and consideration of all the relevant literature – not just the cherry-picked stuff. Yes, this is difficult and never works perfectly but that discipline certainly helps.

An honest approach requires one to approach the scientific literature more objectively and intelligently than anti-fluoridation activists (or activists in general) do. A conscientious approach requires that readers critically assess studies, recognise problems and realise the need to get an overall picture – not a selected one.

I wont deal with the IQ issue, and attempts of fluoridation opponents to implicate fluoride in the “dumbing down” of the population, at this stage because Paul has indicated he will be covering it in a future article. But here are a few comments on the paper of  Xiang et al (2003) which illustrates how Paul places a lot of confidence in a cherry-picked citation.

1. Why did the authors choose to publish in the journal “Fluoride?” It is certainly not considered of high quality. It is actually rather suspect because of the ideological committment of the editors. This gives the impression that even suspect papers will be published if the story is right. My point is that if I had some credible findings in fluoride chemistry and wished to present a paper to the scientific community for their consideration Fluoride is the last journal I would choose.
2. If I was reviewing this paper for publication I would certainly call on the assistance of a skilled statistician as reviewer and would probably recommend changes as a result. I would ask the authors to clarify their figure 1 and its interpretation as well as explaining the meaning and significance of their “BMC” and “BMCL” and an estimation of the errors in their valaues.
3. Xiang’s paper is a minor piece of evidence – surely it should be objectively considered together with all other publications in this area of research. The fact that it is taken in isolation (except for a few other low quality Chinese studies), and nothing of higher quality or from different regions is considered, makes me suspicious. After all, a number of countries with highly qualified scientists (and activists claiming negative effects) have had many years to look at possible health effects from fluoridation. The fact that more credible papers are not produced is hardly good evidence for the claims made bo anti-fluoride activists. Why would they rely on low quality research if better research supporting their claims was available?

Yet Paul uses Xiang’s paper to authoritatively claim it had “found a threshold at 1.9 ppm for this effect.” (What effect he refers to is unclear.) How reliable is that figure of 1.9 ppm (actually 1.85 or 2.32 ppm F in the paper) –  considering the huge variation in the data points of the Figure 1? (Unfortunately the paper is not a lot of use in explaining that figure – reviewers should have paid more attention.)

This is the problem. Papers are selected and then values are pulled out of them to make assertions or claims that really are not warranted – and certainly not by a balanced reading of the literature.

Disadvantaged children

Having experienced the reality of social disadvantage I am still cynical of many people who claim sympathy. Too often as a child I was blamed for problems I had no control over or told things would be OK when I knew they wouldn’t. My experience showed me that most of those social workers, teachers and health practitioners just had no concept of the reality of my position. How could they – unless they had experienced it themselves.

Things are probably a lot better today – but I am still cynical of many of these assertions.

I feel the same cynicism and helplessness when opponents of fluoridation like Paul Connett  agree on “the need to help disadvantaged children” – and then follow that declaration with arguments about hypothetical situations showing absolutely no idea of the reality of life for disadvantaged children.

Paul suggests my advocacy of fluoridation policies will trap families. “What for example are parents in low-income families supposed to do if they don’t want their children to drink fluoridated water?” – he asks. Well, if he really cared – what about the children suffering horribly from toothache whose parents really don’t have the luxury, the interest or feelings of choice, to think about the details of the water supply they use? It is the plight of those children which sparks my empathy.

Sure, there are a few disadvantaged or low-income families who face decisions involving priority of freedom of choice over social policy. The Catholic families who must find resources to send their children to fee-charging Catholic  schools and not  secular public schools. Or the  religious fundamentalists who refuse to use public hospitals. These people do find the resources if their specific minority freedom of choice issue is really important enough to them. We don’t deny the advantages of secular schools and public hospitals to the rest of society just because of the ideological foibles of a small minority.

The resources required to avoid a public water supply are much smaller and should not be used as an argument to deny the advantages of a social health policy to the rest of society.

Yes, children from disadvantaged backgrounds may well have problems with bad nutrition as well as poor oral health. So let us help them. Let us not deny them the beneficial effects of a well established beneficial social oral health policy on the pretence that it might enhance issues related to poor nutrition. Let’s not even  worry about such a cynical diversion – why not do something about that poor nutrition instead?

I find the idea of refusing a beneficial social health policy to children because somebody has it in their head that it might enhance the problems of poor nutrition very cynical and anti-human. It shows a complete lack of empathy for socially and economically disadvantaged families and their children. It is an argument for standing by and doing nothing. And I am not impressed by Paul’s reliance on reports from India where  high natural levels of fluoride do present problems – a situation very different to those in New Zealand and the US considering the fluoridation issue.

Sorry if I come across harshly on this issue – it is important to me, raises strong feelings in me  and I have seen too many examples of false concern and complete lack of empathy to suppress those feelings. I just think people who raise hypothetical “freedom of choice” issues to oppose beneficial social health policies really have no idea of what it is like for disadvantaged children and their families – or any empathy for their situation.

Nature and focus of debate

I think Paul and I have different concepts of what an exchange of scientific opinion should be like. We discussed this in our initial negotiations and our different approaches were obviously not resolved.

Paul expressed a wish that our exchange be focused on his own arguments, and indeed be limited to, and focused on, the issues raised in his book. I rejected this, arguing this was a discussion between equals. We each have our own points to make, our own data, experience and arguments, and we should do so. Anyway this is a public exchange with involvement of readers who are following the articles and commenting on the issues raised. We are really both aiming our arguments at our readers, not each other.

I do not think either of us should require that the other has one arm tied behind their back in entering an exchange like this. I certainly could not, in good faith, enter into such an “exchange” or “debate.”

Paul was kind enough to send me an electronic copy of his book – I thank him for this. I may review the book (which was highly recommended to me by a few local anti-fluoride activists) when I can find time. The book has also been useful for me in making specific criticisms of his arguments. But at no time have I agreed to limit my part of the exchange to the book.

I can appreciate Paul is proud of his book and therefore wishes to promote it. I can also understand why local opponents of fluoridation also promote the book. But he cannot legitimately demand that my part of the exchange be limited in the way he suggests. It is not my job to sell his book.

A general comment on the use of books in science. Books rarely get the degree of peer review of journal articles, can often be dominated by authors’ biases or hobby horses, and are generally somewhat dated in their content. Hence researchers prefer citing research papers to books. Again, while it is understandable Paul should promote his book to health authorities and experts in NZ, surely he can appreciate that researchers  might not give it the same authority they give research papers. Or have the same high opinion of the books the authors’ naturally have.

In fact, along these lines, I understand that local researchers suggested that Paul submit his work on fluoride, or the reviews of others’ research, to a reputable journal for peer review and publication. I understand he has not responded positively to that suggestion yet.

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Anyone wanting to follow the debate and/or check back over previous articles in the debate can find the list of articles at Fluoride Debate.

See also:

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