Misrepresentation of the new Cochrane fluoridation review

A new fluoridation review was published this week – Water fluoridation for the prevention of dental caries from the Cochrane Oral Health Group. It’s main message is:

“Data suggest that the introduction of water fluoridation resulted in a 35% reduction in decayed, missing or filled baby teeth and a 26% reduction in decayed, missing or filled permanent teeth. It also increased the percentage of children with no decay by 15%. These results indicate that water fluoridation is effective at reducing levels of tooth decay in both children’s baby and permanent teeth.”

So, of course, we now have to put up with anti-fluoridation propagandists as they scurry to misrepresent the review’s findings.

I have written before about how Stan Litras, a New Zealand anti-fluoride propagandist,  indulges in cherry-picking, misinformation and outright distortion  of the science (see for example  Cherry-picking and misinformation in Stan Litras’s anti-fluoride article). Well, he has been at it again – this time putting his talents for misrepresentation to use on the new Cochrane Review.

Stan has issued a press release, using his astroturf vanity project (Fluoridation Network for Dentists) – Gold Standard Fluoride Review Contradicts NZ Advice. He claims that the new review’s:

“findings are completely at odds with last year’s Royal Society review, which our government refers to as justification for promoting fluoridation.”

In fact just not true!

Let’s compare his claims with what the Cochrane review actually reported.

Adult benefits

Stan claims the review “finds the science does not support claims that water fluoridation is of any benefit to adults.” Of course, Stan is implying that the review investigated the situation for adults and found no benefit.

Completely wrong.

The review says:

“No studies met the review’s inclusion criteria that investigated the effectiveness of water fluoridation for preventing tooth decay in adults, rather than children.”

And later:

“Only one of these studies examined the effect of water fluoridation on adults (Pot 1974); the reported outcome for this study was the percentage of participants with dentures. There are no data to determine the effect of water fluoridation on caries levels in adults.”

The Cochrane reviewers just did not have any suitable studies fitting their strict criteria for analysis so they could draw no conclusion on this specific question. However, in the review’s discussion they do mention a comprehensive systematic review (Griffin et al., 2007) which attributed a 34.6% reduction of tooth decay in adults to community water fluoridation. The corresponding figure for studies published after 1970 was 27.2%

Social inequalities

Stan implies the review found that fluoridation did not “reduce social” inequalities.

Completely wrong again.

The review was not able to draw any conclusion related to social inequalities because it just did not have that information. it says:

“There was insufficient information available to find out whether the introduction of a water fluoridation programme changed existing differences in tooth decay across socioeconomic groups.”

The review team did find 3 studies reporting effects of water fluoridation on disparities in caries across social class. However, there were problems with all 3 studies meaning the data was not suitable for further analysis and this  prevented them drawing any conclusions.

Benefits when toothpaste used

Stan claims, or at least strongly implies,  the review indicates that community water fluoridation does not “provide additional benefits over and above topically applied fluoride (such as in toothpaste).”

Again, completely wrong.

The review specifically says:

“Data suggest that the introduction of water fluoridation resulted in a 35% reduction in decayed, missing or filled baby teeth and a 26% reduction in decayed, missing or filled permanent teeth. It also increased the percentage of children with no decay by 15%. These results indicate that water fluoridation is effective at reducing levels of tooth decay in both children’s baby and permanent teeth.”

It goes on to say:

“However, since 1975 the use of toothpastes with fluoride and other preventive measures such as fluoride varnish have become widespread in many
communities around the world. The applicability of the results to current lifestyles is unclear.”

So, it raises the possibility that the current efficacy of community water fluoridation in industrialised countries could be lower. However, they could not draw a conclusion on this because only 30% of the included studies took place after 1975.

The review team did attempt to look at factors such as sources of fluoride “(potential confounders of relevance to this review include sugar consumption/dietary habits, SES, ethnicity and the use of other fluoride sources)” but found this not to be possible:

“However, due to the small number of studies and lack of clarity in the reporting within the caries studies, we did not undertake these sub-group analyses.”

Stopping fluoridation

Stan claims (or at least strongly implies) the review shows claims “that tooth decay increases in communities when fluoridation is stopped” are incorrect.

Wrong again.

The review says:

“There was insufficient information available to understand the effect of stopping water fluoridation programmes on tooth decay.”


“No studies that met the inclusion criteria reported on change in dmft or proportion of caries-free children (deciduous/permanent dentition) following the cessation of water fluoridation.”

The only study the review discussed was that of Maupome et al., (2001). This paper is often quoted by anti-fluoridation propagandists but those authors themselves commented on the difficulty of drawing conclusions from their data:

“Our results suggest a complicated pattern of disease following cessation of fluoridation. Multiple sources of fluoride besides water fluoridation have made it more difficult to detect changes in the epidemiological profile of a population with generally low caries experience, and living in an affluent setting with widely accessible dental services.”

Dental fluorosis

Stan claims the review “found that 40% of children in fluoridated areas have dental fluorosis.” However, the review does not compare the prevalence of dental fluorosis in fluoridated areas and unfluoridated areas. It simply draws conclusions about the likely prevalence of dental fluorosis at different fluoride intakes. This lack of comparison is unfortunate, although the omission may be due to the lack of suitable studies that survived their strict criteria.

So Stan’s claim is misleading because, without considering dental fluorosis in the non-fluoridated, areas it is not possible to attribute any responsibility to community water fluoridation. He has simply taken the reported estimate of dental fluorosis for a fluoride intake of 0.7 ppm (the concentration in fluoridated drinking water in NZ) without taking into account the prevalence of dental fluorosis in unfluoridated areas. Very misleading!

The review does, however, calculate estimates of dental fluorosis for different drinking water concentrations and we can draw some proper conclusions from these.

Total dental fluorosis. The review defines this as all the forms of dental fluorosis according to the Dean Index – from questionable to serious. (See Water fluoridation and dental fluorosis – debunking some myths for a discussion of the different forms of dental fluorosis). The graph below shows the reviews findings for the effect of fluoride exposure (drinking water fluoride concentration) on any dental fluorosis.

DF-2True, at 0.7 ppm (the usual concentration for CWF, this shows an estimated prevalence of 40%. But we can calculate the increase due to CWF by subtracting the prevalence for non-fluoridated water. So dental fluorosis due to CWF would be 40% – 33% = 7 % of people  (using the review’s concentration for non-fluoridated water of 0.4 ppm) or 40% – 30% = 10 % of people (using a more realistic concentration of 0.2 ppm).

So Stan is quite wrong to imply CWF causes a total dental fluorosis in 40% of people – it is only 10% or less. However, even that figure is misleading.

Most dental fluorosis is not of aesthetic concern – in fact, the milder forms are often viewed positively from the point of view of the quality of life. So the review also considers dental fluorosis of aesthetic concern – which they define as the serious, moderate and mild forms of dental fluorosis (their inclusion of mild forms here is questionable). The graph below illustrates their findings for these forms of dental fluorosis.

So, if we consider only those forms of dental fluorosis the review considers of aesthetic concern  then calculated prevalence due to CWF amount to only 12% – 10% = 2% of people (using the reviews definition of non-fluoridated) or 12% – 9% = 3%  of people using a more realistic concentration of 0.2 ppm for non-fluoridated.

This is a huge difference to the 40% claimed by Stan.

The review acknowledges that their inclusion of mild forms of dental fluorosis in their definition of dental fluorosis of aesthetic concern is questionable, saying “mild fluorosis may not even be considered an unwanted effect.” Most studies do not consider the mild forms undesirable. It is likely that most of the increase in “dental fluorosis of aesthetic concern” arising from community water fluoridation occurs in the mild forms.  So my suggestion of a 2 or 3% increase in “dental fluorosis of aesthetic concern” will be an overestimation.

It is unsurprising, then, that some cross-sectional studies do not detect any increase in undesirable dental fluorosis attributed to community water fluoridation. The figure below illustrates an example reported in the New Zealand in the 2009 New Zealand Oral health Survey (see Our Oral Health).


Once again this anti-fluoridation propagandist has been caught misrepresenting the scientific literature on this issue. And his misleading press release is being touted as gospel truth by anti-fluoridation groups in NZ and the USA.

It is pathetic such people have to resort to misrepresentation in this way. Surely it is a sign of desperation to use statements that no conclusions were possible on specific details (adult benefits, social inequalities, influence of toothpaste, and what happens when fluoridation is stopped) because no studies fitted the selection criteria as “evidence” that there is no effect.


Griffin SO, Regnier E, Griffin PM, Huntley V. (2007). Effectiveness
of fluoride in preventing caries in adults. Journal of Dental
Research 2007;86(5):410–5.

Iheozor-Ejiofor, Z., Worthington, HV., Walsh, T., O’Malley, L., Clarkson, JE., Macey, R., Alam, R., Tugwell, P., Welch, V., Glenny, A. (2015). Water fluoridation for the prevention of dental caries (Review). The Cochrane Library, (6).

Maupomé, G., Clark, D. C., Levy, S. M., & Berkowitz, J. (2001). Patterns of dental caries following the cessation of water fluoridation. Community Dentistry and Oral Epidemiology, 29(1), 37–47.

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43 responses to “Misrepresentation of the new Cochrane fluoridation review

  1. Steve Slott

    Thank you, Ken. I saw Listra’s “press release” and was irritated that there was, predictably, no opportunity to comment on his gross misrepresentation of this review. If I were he, I would not have wanted any comments either. Undoubtedly, as we speak, Connett is doing the same on an ABC TV news show.

    Steven D. Slott,,DDS


  2. It’s a joke – Connett’s crowd are now listing the Cochrane Review as the 3rd thing on their list which is making it a bad year for those taking a scientific approach to the fluoridation issue.

    Third after the papers on hypothyroidism and ADHD.

    Pretty pathetic, isn’t it?


  3. Steve Slott

    It is pathetic, Ken. Thanks for your constant exposure of the fallacies of these frauds. There are many in the US who are aware of and truly appreciate your efforts.

    Steven D. Slott, DDS


  4. T A Crosbie

    What is pathetic is the failure of you gentlemen of knowledge and education to recognise the thrust of the review is the lack of evidence it reveals. I have been trying to get research based evidence from proponents of fluoridation and all I get is name-calling and vitriol along with references to reviews such as the York one which covers material mainly produced during the 1940s and 50s. The brutal truth is that until the research being called for by virtually every review conducted over the past 30 years has not been done and reliance on evidence that even many in the medical and dental fraternity are increasingly calling into question is ridiculous and probably dangerous.
    I know from personal experience that since I stopped ingesting fluoridated water about two and a half years ago my health has markedly improved and my oral health has not been an issue. Why then should I promote adding HFA to drinking water?


  5. Trev, your anecdotal story would not pass the strict criteria required for the Cochrane review – so I hope you understand why it wan’t considered.

    However, with the studies that did pass that criteria there was clear evidence of the efficacy of CWF. That research was definitely done – even if you and your mate Stan are too blind, or too biased, to see it.

    The misrepresentation and lies employed by Stan are just pathetic.

    The review did not include cross-sectional studies – which is a pity as most recent studies will have fallen into that category given the length of time fluoridation has existed. However, the review did include a discussion on the nature of this sort of research and why the quality consistently gets rated low. But in the real world we have to work with what is possible – we cannot treat people like rats which would be required for the double blind randomised trials you guys pretend to ask for.



  6. In addition to the points about fluorosis so clearly made above, it is important to remember that these mild forms of enamel fluorosis are positively beneficial. The caries protection of fluorosis in a 1st molar is equal to placing and maintaining 1-3 sealants – see Iida and Kumar (2009).

    Further, enamel fluorosis has no negative impact on the quality of life while cavities have a huge negative effect. . . see Do (2007), Onoriobe et al (2014) and Chankanka et al (2010).


  7. Trevor, antifluoridationists are constantly calling for trials on optimal level fluoride to determine its safety, having no idea as to what it is they want tested for safety, because they, like you, have no comprehension of the science of fluoridation. In all likelihood, the vast majority of them have no idea as to what even is a randomized controlled trial. They, like you, simply call for this because they have lazily gleaned the term from antifluoridationist websites, without bothering to take the time and effort required to learn basic facts about fluoridation, what constitutes a RCT, or if such trials are even possible for fluoridation.

    Cochrane did not address safety to any real extent, simply effectiveness, and I strongly suspect this review had a significant amount of bias itself, against fluoridation, given the number of times it continued to unnecessarily mention “bias”, after it had already made that point. Nertheless, even with this apparent bias, this review still affirmed the effectiveness of fluoridation in the prevention of dental decay in children, and simply reported that there was insufficient data meeting its criteria for inclusion in its considerations, in order for it to assess effectiveness in adults or in regard to social inequalities.

    Until you learn at least the basic facts of fluoridation your personal call for “researched based evidence” is meaningless, and would be never-ending, regardless of how much valid evidence was presented to you. In regard to “name-calling”, I suspect you are erroneously claiming valid criticism of your arguments to be personal attacks on you.

    Steven D. Slott, DDS

    Liked by 1 person

  8. Cherry-picking – or its synonymous variations – is practiced on both sides of the fluoridation debate.

    As for cherry-picking from the latest (2015) Cochrane Review on water fluoridation, “The review authors assessed each study included in the review for risk of bias (by examining the quality of the methods used and how thoroughly the results were reported) to determine the extent to which the results reported are likely to be reliable. This showed that over 97% of the 155 studies were at a high risk of bias, which reduces the overall quality of the results.” (Shockingly, that means that less than 3% of the studies used in the Cochrane Review weren’t at “high risk of bias”.)

    Also, the review authors wrote, “Our confidence in the size of effect shown for the prevention of tooth decay is limited due to the high risk of bias in the included studies and the fact that most of the studies were conducted before the use of fluoride toothpaste became widespread.”

    Though I fail to see why bias would enter into any study merely because it was conducted before the use of fluoride toothpaste was widespread. I would have thought that a more accurate assessment of water fluoridation could be made if fluoride was not so widespread from another source.


  9. Thanks, Blossom, for bringing up this issue of “risk of bias” and research quality as it is a straw that many anti-fluoride propagandists will clutch at.

    Firstly you need to understand the limitation impose by the criteria used in this review.

    “For caries data, we included only prospective studies with a concurrent control, comparing at least two populations, one receiving fluoridated water and the other non-fluoridated water, with at least two points in time evaluated. Groups had to be comparable in terms of fluoridated water at baseline. For studies assessing the initiation of water fluoridation the groups had to be from nonfluoridated areas at baseline, with one group subsequently having fluoride added to the water. For studies assessing the cessation of water fluoridation, groups had to be from fluoridated areas at baseline, with one group subsequently having fluoride removed from the water.”

    Secondly, the concept of “bias” used in the review must be understood – you get the wrong impression by relying on “common sense” meanings:

    “we aimed to assess all included studies (including those from the previous review by McDonagh 2000) for risk of bias using the Cochrane ’Risk of bias’ assessment tool adapted for non-randomised controlled studies (Higgins 2011). The domains assessed for each included study included: sampling, confounding, blinding of outcome assessment, completeness of outcome data, risk of selective outcome reporting and risk of other potential sources of bias. We did not include random sequence generation or allocation concealment, as these were not relevant for the study designs included and are covered by the domain for confounding. We had identified the following factors as important confounders for the primary and secondary outcomes: sugar consumption/dietary habits, SES, ethnicity and the use of other fluoride sources.”

    Finally, you must realise these studies are real-world ones – with warts and all, and should be aware of the impossibility of producing “theoretically correct” types of studies with humans (as opposed to rats):

    “there has been much debate around the appropriateness of GRADE when applied to public health interventions, particularly for research questions where evidence from randomised controlled trials is never going to be available due to the unfeasibility of conducting
    such trials. Community water fluoridation is one such area.”

    “The quality of the evidence, when GRADE criteria are applied, is judged to be low. However, we accept that the terminology of ’low quality’ for evidence may appear too judgmental. We acknowledge that studies on water fluoridation, as for many public health interventions, are complex to undertake and that researchers are often constrained in their study design by practical considerations. For many public health interventions,
    the GRADE framework will always result in a rating of low or very low quality. Decision makers need to recognise that for some areas of research, the quality of the evidence will never be ’high’ and that, as for any intervention, the recommendation for its use depends not just upon the quality of the evidence but also on factors such as acceptability and cost-effectiveness (Burford 2012).”


  10. Steve Slott

    Blossom, your statement, “I would have thought that a more accurate assessment of water fluoridation could be made if fluoride was not so widespread from another source.” hits on exactly the reason why the early studies on effectiveness of fluoridation were probably the most accurate. At the beginning, the halo effect, and other confounding factors were not significant yet, so accurate segregation of fluoridated versus non-fluoridated populations for purpose of study, was far easier to attain than it is now. The early findings of 40-60% decay reduction in fluoridation are,in all likelihood, the most accurate assessment we will ever attain.

    Steven D. Slott, DDS


  11. But Steve, if only those who do the oral health studies and those who promote fluoridation would also publicly (and in Abstracts) express the differences (fluoridation vs nonfluoridation) in absolute terms (mean average dmfs / DMFS / dmft / DMFT) instead of percentages, then people – including decision makers – who have no access to the actual studies could see for themselves how they are being hoodwinked. i.e. 45-60% could represent in absolute terms no more than one tooth surface or less than one-quarter or one-half of one tooth.

    Brunelle & Carlos (1990 I think) expressed the difference (c 39,000 children representing more than 43 million children) as 18%. The absolute overall mean average difference was 0.6 of one tooth surface.

    Had delay in tooth eruption from fluoride exposure been taken into account then there might have been a negative result for water fluoridation.

    Queensland’s premier claimed about a 60-65% difference (Townsville vs Brisbane). She cherry-picked just one age group. Had she chosen another specific age group the absolute difference was greater but she chose the one she did because the percentage difference was greater.

    No doubt an advisor of hers chose the figure for her.


  12. Steve Slott wrote | June 21, 2015 at 3:45 pm | “Blossom, your statement, “I would have thought that a more accurate assessment of water fluoridation could be made if fluoride was not so widespread from another source.” hits on exactly the reason why the early studies on effectiveness of fluoridation were probably the most accurate. At the beginning, the halo effect, and other confounding factors were not significant yet, so accurate segregation of fluoridated versus non-fluoridated populations for purpose of study, was far easier to attain than it is now. The early findings of 40-60% decay reduction in fluoridation are, in all likelihood, the most accurate assessment we will ever attain.”

    Steven, when you take into account that more than 97% of the studies used by Cochrane, 2015 were a high risk of bias, that shows even the results of those included studies from when fluoride toothpaste was not so widespread are not to be relied upon.

    If that is the case, why should others believe the so-called benefits of fluoridation that were reported; but not the adverse effects (dental fluorosis 12% of ascetic concern; and c 40% DF overall)?

    To ignore the fact that c 40% in the study had some form of dental fluorosis (evidence of chronic fluoride toxicity) is reprehensible.

    How can you justify that?


  13. KEN WROTE: “Completely wrong again.

    The review was not able to draw any conclusion related to social inequalities because it just did not have that information. it says:

    “There was insufficient information available to find out whether the introduction of a water fluoridation programme changed existing differences in tooth decay across socioeconomic groups.”

    The review team did find 3 studies reporting effects of water fluoridation on disparities in caries across social class. However, there were problems with all 3 studies meaning the data was not suitable for further analysis and this prevented them drawing any conclusions.”

    If reliable data was not available ‘for further analysis (related to social inequalities from fluoridation), how come fluoridation is promoted as reducing social inequalities?

    Surely, Cochrane, 2015 would have included ‘suitable’ studies for analysis of social inequalities if any had been published. After all, Cochrane, 2015 was supposed to be getting at the truth of the matter so it could reliably inform Australia’s National Health & Medical Research Council which has another fluoridation review underway.


  14. Blossom, I have already mentioned the fact that the Cochrane review did not include cross-sectional studies. Their strict exclusion policy is the reason they did not have studies to draw a conclusion.

    However, there are studies out there and conclusions are commonly drawn – the review even mentions them in their discussion.

    The fact is the strict restriction on choice of studies included limits the usefulness of this review to policy makers. I am sure the Australian reviewers will not be so restrictive.


  15. Steve Slott


    1. I am constantly amazed by antifluoridationists who continue to attempt to make barely detectable mild dental fluorosis into a major disorder, yet callously disregard the lifetimes of extreme pain, debilitation, black discoloration and loss of teeth, development of serious medical conditions, and life-threatening infection, directly resultant of untreated dental decay which can be, and is, prevented by water fluoridation. The real question is…….how do you justify condemning people to this because you are “concerned” about such a non-issue as mild dental fluorosis? In 33 years of practicing dentistry in a fluoridated community surrounded by fluoridated communities, I have as yet to see one single case of dental fluorosis attributable to dental fluorosis which could even be detected outside of close examination in my dental chair.

    2. Beause you refuse to take the time and exert the minimal amount of effort to obtain studies, does not mean that they are not available. Decision makers have as much access to the actual studies as do I, or anyone else. The problem with antifluoridationists is that they are too lazy to seek out, read, and attempt to properly understand these studies, instead being content to be spoon-fed the misrepresented results, and out-of-context quotes plucked from these studies, located on little antifluoridationist websites and blogs. An increasing number of antifluoridationists are now citing Connett’s “Second Look” site which is full of titles of studies, I suppose expecting readers to simply accept their nonsense because there are countless studies in the literature which have the word “fluoride” in them somewhere.

    3. Even if one accepts the antifluoridation skewing of Brunnelle and Carlos data, 0.6 of a tooth surface equals 1 tooth surface. Decay doesn’t stop at some boundary line located on a tooth surface. Untreated dental decay in but one tooth surface can, and does cause the lifetimes of effects I noted in #1. People have died as a direct result of untreated dental decay in but one surface of one tooth.

    4. The “delayed eruption” theory has no merit.

    A). “Conclusion: Exposure to fluoride in drinking water did not delay the eruption of permanent teeth. The observed difference in dental caries experience among children exposed to different fluoride levels could not be explained by the timing of eruption of permanent teeth.”

    ——-J Public Health Dent. 2014 Aug;74(3):241-7. doi: 10.1111/jphd.12053. Epub 2014 Mar 17.
    Does fluoride in drinking water delay tooth eruption?
    Jolaoso IA1, Kumar J, Moss ME.
    © 2014 American Association of Public Health Dentistry.

    B). “The present study indicates that the impact of any of the four fluoride exposure parameters on permanent tooth emergence was relatively minimal. Caries experience in the primary molars had a more pronounced impact on the timing of emergence of the successors than exposure to any of the four fluoride parameters.”

    ——Leroy R, et al. (2003). The effect of fluorides and caries in primary teeth on permanent tooth emergence. Community Dentistry and Oral Epidemiology 31(6):463-70.

    C). “Nearly 57000 children (aged from 4 years, 4 months to 15 years, 9 months) of Karl-Marx-Stadt (1.0 ppm F) and Plauen (0.2 ppm F) were examined to compare the mean eruption times of permanent teeth before and after 12 years of water fluoridation. Whereas a direct influence of internally administered fluorides is to be excluded, an indirect action on the premolars may be assumed with certainty. The delayed eruption of all premolars in children of the area with optimally fluoridated water was the only systematic effect which could be detected. This normalization is explained by a prolonged stay of the deciduous teeth in the dental arch which is due to a lesser caries prevalence.”

    ——Kunzel VW. (1976). [Cross-sectional comparison of the median eruption time for permanent teeth in children from fluoride poor and optimally fluoridated areas] Stomatol DDR. 5:310-21. (See abstract)

    D). “However, while there is well established evidence of differences in dental development at similar ages across cultural and ethnicity groups, there is not evidence that water fluoridation is a cause of differential tooth eruption. Information recently published by the Fluoride Action Network based on Australian data, suggesting a substantial difference in tooth eruption between fluoridated and non fluoridated areas of Australia, have been confirmed as being based on erroneous data.”

    “The Australian research centre (ARCPOH) responsible for these data have confirmed the data error and reported that when the error is corrected there is little variation in the number of permanent teeth present at each age between children in Queensland and all of Australia.”

    —–National Fluoridation Information Service (2011): Does Delayed Tooth Eruption Negate The Effect of Water Fluoridation? National Fluoridation Information Service Advisory June 2011, Wellington, New Zealand.

    3. “When you take into account that more than 97% of the studies used by Cochrane 2015 were a high risk of bias” …..” is an inaccurate assessment. Because Cochrane decided that these studies met its definition of “high risk of bias” does mean that they were at high risk to be so, or that they were biases. It simply means that the Cochrane reviewers deemed them to be. Science is based upon consensus opinion. What one particular study may conclude, does not mean that this conclusion has been “proven”, or that it is even accurate. It simply means that this conclusion has been reached by the authors of that particular study, a conclusion which should be included in consideration of the overall body of valid scientific evidence on that issue. Antifluoridationists are notorious for plucking infomation from the literature, quoting it out-of-context, and putting it forth as “proof” of their claim.

    Steven D. Slott, DDS


  16. Blossom, read my article above. 40% occurence of dental fluorosis is not evidence of chronic toxicity as that sort of level, or close to it, is what we see with unfluoridated situations. The increase attributed to adjusting the natural levels of fluoride is very small, often negligible, and occurs in the mildest forms which are usually judged positively for their effect in quality of life.

    Use of the 40% figure in the way you do is just dishonest scaremongering. And that is reprehensible.


  17. Ken – a point of clarification please. Is there a difference between adjusting the natural levels of fluoride and adjusting the levels of natural fluoride and what do you mean by levels?
    Also what is the difference between dose and concentration?


  18. What is your context, Trev? What is your concept of “natural fluoride” and how does that differ from “fluoride?”

    Giving you some leeway here as people use the term “fluoride” quite inappropriately at times.

    Surely you understand the difference between dose and concentration even if your understanding of chemistry is limited, – I shouldn’t have to explain that to you.🙂



  19. I find that people who answer a question with a question are generally obfuscationists. The context of my question is in your response to blossom and the question was, I thought, unambiguous and simple. You are right that my understanding of chemistry is limited hence my questions to someone who claims to know it all.


  20. Why avoid the request for clarification, Trev? What do you understand by “natural fluoride” and how does this differ from your understanding of the word “fluoride?”

    In my understanding, and in this context of “fluoride” in drinking water I understand the word to mean the hydrated fluoride anion. There is no difference between theses anions whatever the source – “natural” are added during treatment.

    Now, perhaps you could either take issue with that ( and in the process take on the understanding of all chemists) or you could clarify the meaning of your terms in your question.

    That is if it is an honest question.🙂



  21. Is there a difference between adjusting the natural levels of fluoride and adjusting the levels of natural fluoride

    1) “natural levels” are those occurring in a source not interfered with by humans. That is, the adjective “natural” relates to the term “level”. Therefore, as soon as they are adjusted by human intervention the resulting level is no longer natural.

    2) “natural fluoride” – here the adjective “natural” relates to the term “fluoride”. As such, it is essentially a loaded and nonsense term. The phrase is useful only if you presume the adjective relates to the source of the fluoride rather than the substance itself, as fluoride is always fluoride, regardless of source. Therefore any adjustment of fluoride levels is an adjustment of “natural” fluoride. If you take issue with this, you are welcome to explain the physical and chemical differences between the “natural” and “unnatural” fluoride ions.

    Trevor, I hope that helps, don’t be reticent should you require further help with comprehension and grammar,


  22. In a 16 February 2012 letter, Charlie Holt, E.I. (District 1 Engineer, ADH Engineering Section, Arkansas Department of Health) informed James Allison (Office Manager and Operator, Carroll-Boone Water District, Eureka Springs, Arkansas) of the following:

    “… Potential impurities in fluoride chemicals include but are not limited to arsenic, lead, and radionuclides…”

    Whatever impurities are in any fluoridating agent end up in public drinking water supplies regardless of any disassociation of individual ingredients.


  23. “Is there a difference between adjusting the natural levels of fluoride and adjusting the levels of natural fluoride.”

    Naturally-occurring fluoride is calcium fluoride (CaF). The three fluoridating agents permitted for use in water supply are euphemistically called “fluoride” but are different products: i.e. sodium fluoride (NaF); hydrofluorosilicic acid (H2SiF6) and sodium fluorosilicate (Na2SiF6).

    The latter two are collected in pollution scrubbers (generally of the phosphate fertilizer industry) to prevent their escape into the environment where they could damage the soil, crops, stock, humans, flora and fauna.

    The unrefined product H2SiF6 is so corrosive that it is generally delivered in rubber-lined tankers. This raw product can eat through concrete.

    Na2SiF6 is a dry product as generally is NaF.

    “Fluorodose” is NaF which is distributed for use in small packages where it is used in small communities that only cater for a small number of people. Package and all are dissolved in the drinking water and the unfortunate people unwittingly drink the dissolved packages as well.

    Even natural fluoride (CaF) can be harmful at very low levels for people who are poorly nourished.

    Ken, you can show that you are open to unbiased debate by allowing this to be published.


  24. Looks like Trev is another satisfied customer – he appears to be happy with the advice he received here on chemistry and grammar.

    Now for Blossom:

    1: The most sensible interpretation of Trev’s question is that he was asking about “fluoride” in solution, in drinking water. After all one can talk about the “level” or “concentration” in solution – but not about the “level” of a solid.

    2: “Naturally” occurring “fluoride” occurs in the solid state as several different minerals, one being calcium fluoride (CaF2 not CaF). Another being apatites – similar to teeth and bones which “naturally” contain fluoride.

    3: The use of the term “natural” is very misleading if it is meant to imply something good. “Natural,” raw caF2 ore would not be acceptable as a fluoridating agent – if only because of the impurities it “naturally” contains. The levels of impurities for water treatment are controlled by regulations. A suitable form of CaF2 would only be produced after dissolution in acid and precipitation of CaF2 from the HF produced. I guess one would not call this manufactured material “natural” – but it is far safer than the original material.

    You can see why terms like “natural” and “artificial” are very misleading.

    4: CaF2 just does not exist in solution – in drinking water. The solid must break up to dissolve and the constituent anions and cation exist independently. The “fluoride” in drinking water exists as the hydrated fluoride anion – whatever its starting material, CaF2, NaF, fluosilicates or fluorosilicic acid (the later 2 decompose on dilution to form silica and the hydrated fluoride anion – fluorosilicates cannot exist in water at low concentrations).

    5: Concentrated chemicals are often corrosive and toxic – nothing new there. that is why there are material data sheets advising those who handle, transport, dispose of or manufacture concentrated chemicals of the regulations involved. Such material data sheets are irrelevant ot drinking water – and only an ignorant person, or someone wishing to misinform or scaremonger, would use them in a discussion of community water fluoridation.


  25. Blossom – it is easy to present misleading claims on impurities in fluoridating chemicals if your intention is to scaremonger. However, the level of impurities is regulated and this graph shows how the measured levels (taken from 16 Australian certificates of analysis for fluorosilicic acid) compare with the regulated maxima.
    impurities in fluoridating chmeicals

    You can read more at Fluoridation: emotionally misrepresenting contamination

    You also need to put such impurities into context with those present ion the “natural” water sources used. T^his graph compares the “natural” levels of arsenic in the water source used for my city to that contributed by fluoridating chemicals.
    Hamilton Water

    You can read further at Fluoridation: putting chemical contamination in context


  26. T A Crosbie

    And how does your smart-arse remark about comprehension and grammar contribute to the debate?


  27. Chemistry and grammar – Trev. However, you do seem satisfied.🙂


  28. I commented on comprehension and grammar.

    Trevor, you asked

    Is there a difference between adjusting the natural levels of fluoride and adjusting the levels of natural fluoride

    which is indicative of confusion (non-comprehension) of the terms natural levels of fluoride and levels of natural fluoride. The confusion disappears when the grammar is understood.


  29. Researchers, including New Zealand scientist Dr Linda Gulliver, have released findings into possible links between common chemicals and the development of cancer.
    Their results, published in the journal Carcinogenesis, show mixtures of chemicals used in our environment may be acting in concert with each other inside the body to trigger the disease.
    Gulliver, from Otago University’s faculty of medicine, says on the back of the findings of the Halifax Project, “considerable attention” needs to be given to investigating the concerning links.
    A high-profile taskforce was formed in 2013 by the international organisation Getting to Know Cancer, which was concerned that cancer research was focused primarily on the role of heritable and lifestyle factors as triggers.
    This is despite evidence that as many as one in five cancers may be caused by chemical exposures in the environment that are not related to personal lifestyle choices.
    Chemicals are tested for carcinogenic links, but only one at a time, leaving questions around the possibility that a fusion of these chemicals may instead be causing cancer.
    The taskforce of 174 scientists in 28 countries investigated 85 prototypic chemicals that were not considered to be carcinogenic to humans, and they reviewed their effects against a long list of mechanisms that are important for cancer development.
    Working in teams that focused on various hallmarks of cancer, the group found that 50 of those chemicals examined supported key cancer-related mechanisms at levels at which humans are routinely exposed.
    The finding supports the idea that chemicals may be capable of acting in concert with one another to cause cancer, even though low-level exposures to these chemicals individually might not be carcinogenic.
    Lead researcher William Goodson III, from San Francisco’s California Pacific Medical Center, said his results show one-at-a-time testing is out of date and must be modernised.
    Ken and Steve – I am sure that you will be interested in the above given that you both have open minds on the issue of chemicals in the water. Regards,Trev


  30. Facinating Trevor. Chemicals in the environment can cause cancer. What a startling discovery.

    Of no relevance to optimally fluoridated water, however.

    Steven D. Slott, DDS


  31. T A Crosbie

    Unlike you Steve I look at medical science not the biased studies you dogmatically proclaim as proof the CWF is safe, beneficial and cost effective.
    You may be a dentist but you are also a zealot!


  32. Excuse my French, but Trev looking “at medical science not the biased studies” my arse. Trev wouldn’t recognise a medial study if he tripped over it.

    He has simply used copypasta of a newspaper article – unattributed as usual. And attempted to draw unwarranted conclusions.

    It is scatty attempts at scaremongering like this that explain why his silly attempt to use the High Court to prevent Hamilton reintroducing fluroidation was bound to fail. Even that was obvious to him after an initial blast of publicity – so obvious he retreated.


  33. He has simply used copypasta of a newspaper article – unattributed as usual.

    (rolls eyes)
    The clown called Trevor is incapable of learning.

    For what it is worth, here is the article.

    The Guardian.
    23 June 2015

    Exposure to mixture of common chemicals may trigger cancer, scientists find


  34. Steve Slott

    What a comfort….knowing that Trevor is on top of all the latest medical science, keeping us fully informed at all times…….

    Steven D. Slott, DDS


  35. I’m afraid you made the common error of confusing incidence with prevalence and the common error of confusing a percentage point increase for a percentage increase.

    You wrote:

    “True, at 0.7 ppm (the usual concentration for CWF, this shows an incidence of 40%. But we can estimate the increase due to CWF by subtracting the incidence for non-fluoridated water. So the increase due to CWF would be 7% (using the review’s concentration for non-fluoridated water of 0.4 ppm) or 10% using a more realistic concentration of 0.2 ppm.”

    The graph you derived the numbers from uses prevalence data, not incidence data. Prevalence includes all cases, incidence includes only new cases in a time period of interest.

    In this case, 7 and 10 are percentage point increases. But the 7 percentage point increase is actually an increase from 33% to 40%. Divide 7 by 33 and you find that 40 represents a 21% increase in prevalence.

    So this statement has the wrong figure and it should not imply the increase concerns risk since it’s based on prevalence rather than incidence data:

    “So Stan is quite wrong to imply CWF causes a total dental fluorosis increase of 40% – it is only 10% or less. However, even that figure is misleading.”

    You continued:

    “So, if we consider only those forms of dental fluorosis the review considers of aesthetic concern then increases due to CWF amount to only 2% (using the reviews definition of non-fluoridated) or 3% using a more realistic concentration of 0.2 ppm for non-fluoridated.”

    Again 2 and 3 are percentage point increases on the graph. The correct percentage increases (in prevalence) are 33% and 20% respectively.


  36. Thanks for your comment, William.

    I agree I often use the words incidence and prevalence as commonly indicating the same thing, but I will go through and change to prevalence as this is the term usually used for actual measurements (and is used in the Cochrane review).

    To be absolutely correct, though, the data presented is for probability – a calculated estimate rather than measured prevalence. However, I felt that, while correct, would introduce an unwarranted level of confusion.

    As for use of percentages. These can always be confusing and, as you say, I am using changes in percentage points rather than calculating a new percentage which would certainly be confusing and certainly not what I intended. It would also be meaningless for this particular discussion. I felt this was obvious from the context – but again I will have a look to see if it needs clarification.


  37. Ken, you made a calculation by subtraction. For what you described, the proper calculation involves division. Percentage increase makes a comparison in relative terms (which is of etiologic significance when using incidence data). Percentage point increase makes a comparison in absolute terms (and measures impact when using incidence data).

    See https://xkcd.com/985/ for the importance of being clear.


  38. Yes, William, your point has already been taken and I was well aware of the confusion created by using percentages (the presentation in the Cochrane review as a prevalence due to fluoridation, and the way this is peddled by motivated activists, certainly underlines the rampant confusion possible). As I said I believe the context makes this clear (especially as the probabilities are presented graphically) – and, as I said, I will have another look and see if more clarification is required (as you, at least, seem to have taken the wrong message).

    Any comments on the actual post itself, though?


  39. T A Crosbie

    The Cochrane Collaboration, a group of doctors and researchers known for their comprehensive reviews—which are widely regarded as the gold standard of scientific rigor in assessing effectiveness of public health policies—recently set out to find out if fluoridation reduces cavities. They reviewed every study done on fluoridation that they could find, and then winnowed down the collection to only the most comprehensive, well-designed and reliable papers. Then they analyzed these studies’ results, and published their conclusion in a review earlier this month.
    The review identified only three studies since 1975—of sufficient quality to be included—that addressed the effectiveness of fluoridation on tooth decay in the population at large. These papers determined that fluoridation does not reduce cavities to a statistically significant degree in permanent teeth, says study co-author Anne-Marie Glenny, a health science researcher at Manchester University in the United Kingdom. The authors found only seven other studies worthy of inclusion dating prior to 1975.
    The authors also found only two studies since 1975 that looked at the effectiveness of reducing cavities in baby teeth, and found fluoridation to have no statistically significant impact here, either.
    The scientists also found “insufficient evidence” that fluoridation reduces tooth decay in adults (children excluded).
    “From the review, we’re unable to determine whether water fluoridation has an impact on caries levels in adults,” Glenny says. (“Tooth decay,” “cavities” and “caries” all mean the same thing: breakdown of enamel by mouth-dwelling microbes.)
    “Frankly, this is pretty shocking,” says Thomas Zoeller, a scientist at UMass-Amherst uninvolved in the work. “This study does not support the use of fluoride in drinking water.”

    Again the above re-iterates the oft repeated call in study after study of the need for valid research into fluoridation. The mantra adopted in the 1960s that fluoridation is ‘safe, beneficial and cost effective’ no longer has the bite it once had. The weight of evidence is shifting and once a tipping point is reached the pro fluoride lobby will be history. The sooner the better!


  40. Trev, you are at it again. You see something on one of your pet fluoride free page and then present us with unattributed copypasta. You are pathetic!🙂

    Why don’t you actually have a read of the Cochrane report? You might then find out that this Newsweek article is also pathetic.

    It is aurely pathetic to take a review which reports that CWF

    “resulted in a 35% reduction in decayed, missing or filled baby teeth, and 26% reduction in decayed, missing and filled permanent teeth.”

    And then claim the review found no statistically significant reduction in decay of permanent teeth. And falsely attribute that claim to one of the authors!

    If you read this sort of rubbish for you information, Trev, no wonder you are so ignorant on the subject.🙂



  41. T A Crosbie

    I know what has happened to my health since I stopped ingesting fluoridated tap water and if that has made me ignorant of the safety and benefits of the practice then I admit to being ignorant but happily so. I don’t understand why you and your small cabal of zealots want NZ to join with the statistically insignificant number of nations who still add a by-product of fert manufacturing to their people’s water regardless of any disbenefit or damage to the individuals concerned.
    As one placard stated “F off”


  42. Steve Slott


    Ever hear of the “placebo effect”………

    Steven D. Slott, DDS


  43. So, Trev, the “medical studies” you claim to rely on turn out to be personal hypochondria!



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