Cochrane review: Fluoridation reduces caries in kids’ teeth
By Donna Domino, Features Editor
July 16, 2015 — Fluoridation is effective at reducing levels of caries in children’s teeth, according to a new review in the Cochrane Library (June 18, 2015). But the researchers concluded there is not enough information to determine whether the introduction of fluoridation programs changed existing differences in caries across socioeconomic groups.
Caries is a major public health problem in most industrialized countries, affecting 60% to 90% of schoolchildren, the review authors noted. Community water fluoridation in the U.S. began in 1945; nearly 75% of Americans who use public water systems now get fluoridated water, according to the review. Fluoridation systems are currently used in about 25 countries worldwide.
Fluoride — which occurs naturally in the soil, water, and atmosphere — is also available in most toothpastes, and it can be provided as an extra preventive measure through products such as mouth rinses, varnishes, and gels.
“Community water fluoridation … is the best method of delivering fluoride to all members of the community, regardless of age, education, income level, or access to routine dental care.”
— CDC response to Cochrane review
The U.S. Centers for Disease Control and Prevention (CDC) considers water fluoridation one of the greatest public health achievements in the 20th century. Additionally, the ADA and the American Dental Education Association (ADEA) support and encourage fluoridation of community water supplies, as does the International Association of Dental Research, the National Institute of Dental and Craniofacial Research, and the World Health Organization.
In April, the U.S. Department of Health and Human Services issued a new recommendation for a single level of fluoride in community water systems of 0.7 mg/L (parts per million [ppm]) to maintain caries prevention benefits and reduce the risk of dental fluorosis in community water systems. The previous recommendation was a range of 0.7 mg/L to 1.2 mg/L, issued in 1962.
“Water fluoridation is effective and safe,” said ADA President Maxine Feinberg, DDS, in a statement after the new fluoride levels were announced.
“The change in level recommended allows for these other sources of fluoride intake and will still maintain the protective benefit of fluoride, as well as reduce the likelihood of fluorosis,” AAPD President Edward H. Moody Jr., DDS, told DrBicuspid.com after the announcement.
The American Dental Hygienists’ Association (ADHA) has noted that fluoridated public water systems have significantly improved residents’ oral health.
An unwanted effect of fluoride use is dental fluorosis that is caused when young children, whose permanent teeth are developing, swallow excessive fluoride. This can range from mild white patches on the teeth to severe mottling with brown staining.
In this latest review, Cochrane researchers sought to evaluate the effects of water fluoridation on preventing caries and also assess its effects on dental fluorosis.
They identified 155 studies up to February 2015 that met inclusion criteria in which children receiving fluoridated water, either natural or artificial, were compared with those receiving water with very low or no fluoride. The majority of studies (71%) were conducted prior to 1975 and the widespread introduction of the use of fluoride toothpaste. A further 135 studies examined dental fluorosis.
More than 97% of the 155 studies had a high risk of bias, which reduced the overall quality of the results, the reviewers noted. They also found a substantial variation among studies in terms of their results. Some 107 studies provided sufficient data for quantitative synthesis to be included in the review, the researchers stated.
The reviewers searched Cochrane databases, the U.S. National Institutes of Health Trials Registry, and the World Health Organization’s International Clinical Trials Registry for ongoing trials.
For caries data, the review included only prospective studies with a concurrent control that compared at least two populations — one receiving fluoridated water and the other nonfluoridated water — with outcomes evaluated with at least two points in time. No studies that aimed to determine the effectiveness of water fluoridation for preventing caries in adults met the review’s criteria.
The data suggest that the introduction of water fluoridation resulted in a 35% reduction in decayed, missing, or filled primary teeth and a 26% reduction in decayed, missing, or restored permanent teeth, the review found. It also increased the percentage of children with no caries by 15%.
“Although these results indicate that water fluoridation is effective at reducing levels of tooth decay in children’s baby and permanent teeth, the applicability of the results to current lifestyles is unclear because the majority of the studies were conducted before fluoride toothpastes and the other preventative measures were widely used in many communities around the world,” the reviewers wrote.
“Our results suggest a complicated pattern of disease following cessation of fluoridation,” they concluded. “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.”
Commentary on the review
The CDC pointed out the many benefits that fluoridation provides.
“The biggest advantage of community water fluoridation is that it is the best method of delivering fluoride to all members of the community, regardless of age, education, income level, or access to routine dental care,” wrote Katherine Weno, DDS, JD, in response to the review. Dr. Weno is the director of the Division of Oral Health for the CDC’s National Center for Chronic Disease Prevention and Health Promotion.
Some fluoride supporters said the review’s findings are being distorted by antifluoride groups. “Fluoride opponents are blatantly misrepresenting the report’s findings to dishonestly use the authority of the Cochrane name to support antifluoride campaigns,” Ken Perrott, PhD, scientific advisor for the Making Sense of Fluoride group, told DrBicuspid.com.
He also faulted Cochrane researchers for providing opportunities for “dishonest cherry-picking and distortion, because they did not qualify many of the statements made in the review’s abstract and plain language summary.”
“The exclusion of so many important studies meant the review was unable to come to any conclusions about important aspects like the effect of community water fluoridation [CWF] on socioeconomic difference in tooth decay, the effect of stopping CWF programs on later tooth decay, and the effectiveness of CWF in reducing adult tooth decay,” Perrott added.
The CDC also criticized the reviewers’ “restrictive criteria” for including studies in their analyses. “Although valid, peer-reviewed studies document the effectiveness of community water fluoridation in children and adults even after the use of fluoride toothpaste became widespread, these studies were not considered by Cochrane,” Dr. Weno wrote.
Creating, maintaining and disseminating systematic reviews in oral health
Top of Form
Our response to the feedback on the Cochrane fluoridation review
We welcome the ongoing debate around the Cochrane review on water fluoridation. Whilst we cannot respond to all issues raised individually, there are several themes that have arisen which we feel it would be useful to clarify at this stage.
Firstly, we are sorry that some readers feel that the blog has not accurately represented the review as a whole. We make every effort to ensure that our reporting is transparent. We also want the blog to be accessible to a wide audience and one of the ways we do this is by limiting its length. As a result, the blog is much less detailed than the review itself. We would encourage interested parties to read the full review. The review should be read in full before application of the findings is considered. We should stress that the review is for an international audience. It is not the purpose of a Cochrane review to make recommendations; we aim to present the research evidence in a robust, reproducible, transparent way to inform health care decisions. Those decisions are likely to vary according to setting.
Exclusion of studies
One, recurring criticism of our review is that “97% of the fluoridation research [was] ignored”(Perrott, 2015). This criticism is based on the PRISMA flow diagram which shows our search strategy identified >4500 records (after duplicates were removed) but included only 107 studies in our analyses. Those involved in searching electronic bibliographic databases will be aware that the first search often returns articles that are unrelated to the topic of the search, it is usual in systematic reviewing to discard over 90% of the references initially retrieved (Rathbone, 2014). In order to be as comprehensive as possible in our search, and ensure high sensitivity, we often have to cast our net very wide. Certainly, with searches to identify observational studies (which are often poorly indexed), rather than RCTs, we have to trade off specificity with sensitivity.
The protocol for the Cochrane review, published in December 2013, set out very clear inclusion criteria for the studies to be reviewed with regard to caries. Studies eligible for inclusion needed to have a concurrent control group and they needed to have collected data from at least two points in time, i.e. they could not be single time point, cross sectional studies. We acknowledge that there may be concerns regarding the exclusion of cross-sectional studies from the current review. We gave much thought to the inclusion criteria we used, and, as in the York review, felt cross-sectional studies do not adequately evaluate the effects of water fluoridation on the prevention of dental caries.
Within the discussion of the Cochrane review we consider the role of cross-sectional studies, and highlight previous reviews that have included such studies. For example, the comprehensive review by Griffin et al (2007) that evaluated the effectiveness of fluoride in preventing caries in adults. The review included nine studies that examined the effectiveness of water fluoridation, all of which fell outside the scope of the Cochrane review. Of the nine studies they included, eight were cross-sectional studies, with single time-point data. The review by Griffin et al (2007) demonstrated a caries prevented fraction of 34.6% (95% CI 12.6% to 51.0%), when pooling data from seven studies of lifelong residents of control or fluoridated-water communities. This effect size was still present, but reduced, when the analysis was limited to studies published after 1979 (prevented fraction 27.2% (95% CI 19.4% to 34.3%; 5 studies). The most recent of the post-1979 papers included in the review was published in 1992 and only one study reported evaluating a fluoride concentration that could be considered applicable today (two studies did not report fluoride concentration and two evaluated fluoride concentrations above 1.6 ppm).
It has been suggested that the recent review by Anglemyer et al (2014) strengthens the argument to include cross-sectional studies in our review. The review summarizes the results of methodological reviews that compare the results of randomized controlled trials with the results of from observational studies addressing the same question. Their analyses are predominantly from comparisons of RCTs with cohort or case-control studies. No comparisons were made between RCTs and cross-sectional studies. We acknowledge that there are more recent cross-sectional studies evaluating water fluoridation and caries levels however, we are yet to be convinced of the additional benefit of including single time point, cross sectional studies in our review.
Several readers have raised the issue that two studies, published 15 years ago by a member of the review team (Professor Helen Worthington), have been excluded from our review. These studies evaluated disparities in caries levels across different social groups and, again, were single time-point, cross-sectional studies that did not meet the inclusion criteria for our review. The cross-sectional studies, whilst able to provide information on whether water fluoridation is associated with a reduction in disparities, are not able to address the question of whether water fluoridation results in a reduction in disparities in caries levels. We would not alter our inclusion criteria simply to allow inclusion of our own primary research papers.
It has also been suggested that our inclusion criteria for cessation studies were too restrictive. However, as with the evaluation of the initiation of water fluoridation, the review team felt an appropriate concurrent control was necessary for cessation studies. Our inclusion criteria were set to allow the inclusion of studies where groups under comparison were as comparable as possible at baseline with regard to caries levels and confounding factors.
Inequalities in dental health
Over the past 15 years there has been misinterpretation of the evidence in the York review, McDonagh et al (2000). It is often stated that the York review found some evidence that water fluoridation reduces inequalities between 5 and 12 year olds from different socio-economic groups in their average levels of decayed, missing and filled teeth. This statement does not accurately reflect the evidence in the review. The review did find some evidence that water fluoridation reduces the inequalities in dental health across social classes in five year olds, using the dmft/DMFT measure. Similarly, there was very limited evidence that water fluoridation reduces the inequalities in dental health across social classes in 12 year olds, when measuring DMFT. However, no effect was seen in any of the other age groups evaluated (i.e there is no evidence that water fluoridation reduces inequalities between 5 and 12 year olds from different socio-economic groups). When evaluating the proportion of caries free children there was no evidence from the included studies to suggest that fluoridation reduces disparities across social class.
The authors of the York review have previously raised concerns about the misinterpretation of their findings and, in 2003, issued a statement in which they explicitly state “The evidence about reducing inequalities in dental health was of poor quality, contradictory and unreliable.”
Within the Cochrane review, we felt there were insufficient data to determine whether initiation of a water fluoridation programme results in a change in disparities in caries levels across different groups of people.
There has been discussion around the terminology used within the review with regard to ‘water fluoridation’. We accept that in the fluorosis section of the review it is more appropriate to refer ‘the effects of fluoride in the water’ rather than ‘water fluoridation’ throughout.
Whilst we do not make direct comparison between areas with and without fluoride in the water, we do present the marginal probabilities of dental fluorosis of aesthetic concern and all levels of fluorosis for a range of fluoride concentrations. The data should not be used as ‘proof’ that community water fluoridation causes dental fluorosis in 40% of the population, or dental fluorosis of aesthetic concern in 12% of the population. However, as the review concludes, the evidence does show that there is a significant association between dental fluorosis (of aesthetic concern or all levels of dental fluorosis) and fluoride level. The evidence is limited due to high risk of bias within the studies and substantial between-study variation.
We are grateful to readers of the review for highlighting our omission of the paper by McGrady et al (2012). Despite our comprehensive search and extensive peer review, we apologise that this study was not picked up sooner for inclusion in the review. Whilst it does not meet the inclusion criteria for caries studies, it does contain relevant fluorosis data. We have reanalysed the fluorosis data to include this study, and will update the review in due course. The study does not make a substantial difference to the data, as shown below. The values for fluorosis at 0.7 ppm remain unchanged.
Aesthetic fluorosis, concentrations 5ppm or less
|Fluoride exposure||Probability of fluorosis aesthetic concern (95% CI)|
|0.1||8 (5 to 13)|
|0.2||9 (5 to 13)|
|0.4||10 (6 to 14)|
|0.7||12 (8 to 17)|
|1||15 (10 to 21)|
|1.2||18 (12 to 24)|
|2||31 (23 to 40)|
|4||60 (47 to 72)|
All fluorosis, concentrations 5ppm or less
|Fluoride exposure||Probability of fluorosis (95% CI)|
|0.1||28 (23 to 33)|
|0.2||30 (25 to 34)|
|0.4||33 (28 to 38)|
|0.7||40 (35 to 44)|
|1||47 (42 to 51)|
|1.2||52 (47 to 56)|
|2||68 (63 to 73)|
|4||83 (77 to 89)|
Assessment of Risk of Bias
A bias, in an epidemiological context is a systematic error, or deviation from the truth. The term is widely used with this meaning. While it is appreciated that there are other uses of the word bias, what is meant by bias in the context of the review is detailed in the methods section and appropriate references are given.
We agree that many of the gold standard conditions necessary to completely avoid bias would be very difficult, if not impossible, to achieve for a study looking at water fluoridation. However, just because these biases are inevitable, it doesn’t mean their potential impact on the results of a study can be ignored. Findings must always be assessed critically against how close to the truth they can reasonably be assumed to be. The truth does not make allowances for studies that are practically difficult to conduct.
Assessing the risk of bias of included studies is not about labelling a study as good or bad, it is about objectively assessing how true the findings of a study can be considered to be based on the way in which the study was conducted and reported. The criteria by which a study may be assessed vary according to study type. The risk of bias assessment undertaken within the Cochrane review used criteria relevant to the assessment of non-randomized studies.
Assessing the overall quality of the evidence
The review has received some criticism for its use of GRADE in assessing the overall quality of the evidence. This is an area that we, again, gave much thought to and we detail our thoughts in the review’s discussion. GRADE has developed over recent years as an internationally recognised framework for systematically evaluating the quality of evidence within both systematic reviews and guidelines. As a review team, we feel GRADE is an appropriate method for assessing the overall body of evidence. However, we acknowledge that the terminology used in GRADE relating to ‘quality’ may appear too judgmental. We also 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. In order to overcome these concerns, a decision was made to omit the GRADE terminology of relating to ‘quality’ and discuss the review’s findings in terms of our confidence in the results. This is reflected in the abstract, summary of findings and plain language summary (PLS). Unfortunately, due to word limits for both the abstract and PLS we were unable to include all relevant qualifications. However, we would again stress that those involved in decision making should read the full review and not rely on information presented in abstracts, PLS, blogs, or any summaries of the review.
We thank all those contributing to the discussion around this review. We apologise for not being able to respond to all, individual contributions but will continue to read postings with interest.
Anglemyer A, Horvath HT, Bero L. Healthcare outcomes assessed with observational study designs compared with those assessed in randomized trials. Cochrane Database of Systematic Reviews 2014, Issue 4. Art. No.: MR000034. DOI: 10.1002/14651858.MR000034.pub2.
Centre for Reviews and Dissemination. What the ‘York Review’ on the fluoridation of drinking water really found. University of York, 2003
Griffin SO, Regnier E, Griffin PM, Huntley, V. Effectiveness of fluoride in preventing caries in adults. Journal of Dental Research, 2007, 86(5), 410-415
McDonagh M, Whiting P, Bradley M, Cooper J, et al. A systematic review of public water fluoridation. (York review), 2000, NHS Centre for Reviews and Dissemination, University of York.
McGrady MG, Ellwood RP, Maguire A, Goodwin, M. et al. The association between social deprivation and the prevalence and severity of dental caries and fluorosis in populations with and without water fluoridation. BMC Public Health 2012, 12: 1122
Perrott K. Cochrane fluoridation review. I: Most research ignored. Open parachute, 2015
Rathbone J, Carter, M, Hoffmann T, Glasziou P. Better duplicate detection for systematic reviewers: evaluation of Systematic Review Assistant-Deduplication Module. Systematic reviews 2014, 4: 6.
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- Dr Andrew Harms B.D.S.(Adelaide) on 07/14/2015 at 11:15 said:
The cochrane review into water fluoridation has a very glaring error in that the issue of the effects of fluoridation should have looked at the delay in tooth eruption and its distortion of dmft/DMFT .If the data was age corrected to reflect the delay of approx. one year in tooth eruption then the perceived “benefit ” would not occur.I am astonished that the group missed this most basic issue.
The forced-fluoridation fanatics often try to claim that the low rates of dental caries in western European countries which do not have artificial water fluoridation are due to naturally occurring fluoride in water, or some other kind of artificial fluoridation such as salt fluoridation. They are lying. http://forcedfluoridationfreedomfighters.com/scotland-and-the-netherlands-inconvenient-examples/
From this research scientist and not an epidemiologist, please notice that all the studies accepted for the Cochrane review that claim reduction in dental caries from fluoride water consumption only report percent differences that compare to or are less than measurement error. This means that there is no actual detectable effect whatsoever of ingesting water fluoride on dental caries. Of course this is the conclusion that has already been made from the detailed studies of Ziegelbecker; and the data from Teotia and Teotia; and from Yiamouyiannis. This all adds to the recognized disqualifying attributes of “fluoridation trials” that were fully described in the textbooks by dentist statistician Phillip Sutton. It is important to recognize that the FDA banned the sale of fluoride compounds intended to be ingested by pregnant women in the U.S. in 1966 because detailed data proved no positive effect on teeth caries occurred in offspring born to mothers who participated in fluoride consumption. Richard Sauerheber, Ph.D.
I welcome the willingness of the review authors to engage with those of us who are critical of aspects of the review. So far the response seems over-defensive but hopefully ongoing discussion will overcome se sitivities and help provide solutions to the problems identified.
However, at this stage I want to bring attention to the elephant in the room. The way this review has been misrepresented and its findings distorted by anti-fluoride campaigners and their media in the “natural”/alternative health industry. I believe that the review authors have a responsibility to counter this misinformation. A responsibility because the misrepresentation and distortion is destroying the effectiveness of the review and the credibility of the Cochrane organisation. But also a responsibility because the Abstract and Plain Language Summary have contributed to this misrepresentation and distortion by not properly qualifying many of the statements made. Sure, qualifications were often in the body of the review – but the fact is very few people read that. Unfortunately policy makers and media rely almost completely on abstracts and summaries, and often only on headlines in the media. The authors should not seek to avoid that fact by asking that people read the full text. Surely they can see that is just not responsible.
For example we have a Newsweek article headlined “Fluoridation May Not Prevent Cavities, Scientific Review Shows” ( and there are worse) – the article completely misrepresents the review and provides a mouthpiece for well-known anti-fluoride campaigners to distort the science. This sort of distortion needs countering and the review authors have a responsibility to do this. Unfortunately the defensive tone of this blog post seems more aimed at hiding behind academic principles related to absolute truth, unrealistic expectations of research studies and academic definitions of the meaning of words like “bias” and “quality.”
But that is just not good enough. This review is not an academic exercise. It is meant to relate to the real world. Yes, the review itself does not make recommendations but it will be used by policy makers who are deluged by politically and ideologically motivated campaigners. Inevitably it will be used to make recommendations and decisions about health policies. Unfortunately, because of the misrepresentation of the review and the lack of proper explanation and qualification in the Summary and Abstract (a real godsend to cherry pickers) it is not responsible for the authors to deny they have a responsibility for this.
So a question. What will the Cochrane group and the authors of this review do to counter the current misinformation and misunderstanding?
While I welcome the response in this post to professional criticisms (really a form of peer review which should have occurred before the review was released) I actually think the authors have their priorities wrong. It is far more important for them, for the good name of Cochrane and for those involved in social health issues for the authors at this stage to put those efforts primarily into countering the damaging misrepresentation and distortion.
Fluoridation is based on pseudoscience, which you know because I have asked you many times to cite a single good quality original research study which indicates that the forced-fluoridation experiment is anything but harmful and useless, and you can never come up with anything. Stop squawking and admit the truth.
I am pleased the review authors are undertaking to update the review (“in due course”). Hopefully updating will take into account other comments besides the one referring to omission of McGrady et al (2012). This post accepts that the term “water fluoridation” was used inappropriately in the section on fluorosis. Hopefully this will be amended. I think amendments should also be made to correct misinterpretations of the relevance of the calculations in this section to community water fluoridation. It is hopeful that this post accepts that the section on dental fluorosis did not compare fluoridated and unfluoridated areas – and in principle did not draw conclusions about the effect of fluoridation. It particularly repudiates widespread claims the review’s finding mean the CWF causes the prevalence figures calculated. But, there appears to be confusion because the review is specifically about community water fluoridation effects – but this section is quite unrelated to community water fluoridation effects. Its purpose was simply to derive a relationship between fluoride intake and dental fluorosis prevalence. As such it should not have been included – its subject is quite different. However, the authors seem unaware that by highlighting the dental fluorosis calculations at 0.7 ppm F they are inviting readers to make the incorrect interpretation they specifically reject in saying “The data should not be used as ‘proof’ that community water fluoridation causes dental fluorosis in 40% of the population, or dental fluorosis of aesthetic concern in 12% of the population.” Given the concentration of 0.7 ppm F, and the title of the review itself as connecting it with water fluoridation, I think the authors have a responsibility to correct the text so as to avoid inviting such misinterpretations. Why not do what was done with the caries data – calculate an effect due to fluoridation? Using the calculate prevalence data presented this could be equal to the calculated prevalence at 0.7 ppm (fluoridated) – the calculated prevalence at 0.4 ppm (which the review defines as unfluoridated). That would produce a calculated prevalence of 2% – effectively zero considering the wide CI ranges – (8 to 17) – (6 to 14). Using the calculated prevalence at 0.2 ppm the calculated prevalence due to fluoridation is 3% – still effectively zero. Incidentally, a similar calculation using data from the 2009 New Zealand Oral health Survey (http://www.health.govt.nz/publication/our-oral-health-key-findings-2009-new-zealand-oral-health-survey) shows the prevalence of dental fluorosis of aesthetic concern (as defined by the Cochrane review) as 4.7% in fluoridated areas and 10.1% in non-fluoridated areas (a prevalence due to fluoridation of -5.4%. Given the wide CI range we can see the effect of fluoridation is effectively zero. So, thanks for clarifying the review’s findings about dental fluorosis in this post. But please listen carefully to the way the reviews findings on this issue are being widely misrepresented and consider updating the review to counter this – particularly its Abstract and Plain Language Summary.
- John Teagle on 07/17/2015 at 04:38 said:
The main concern is the review confirms the WHO findings that fluoridation is a contributing factor when contracting the disease known as dental fluorosis caused by an overexposure to fluoride whether it results from ingestion of fluoridation or other food sources or topical application due to oral hygiene products. How can anyone seriously maintain fluoridation is not harmful when it is contributing to a disease as discussed in the following WHO document::
This document states the following about contracting the disease dental and skeletal fluorosis from drinking water as follows:
Water-related diseases Fluorosis The disease and how it affects people Ingestion of excess fluoride, most commonly in drinking-water, can cause fluorosis which affects the teeth and bones. Moderate amounts lead to dental effects, but long-term ingestion of large amounts can lead to potentially severe skeletal problems. Paradoxically, low levels of fluoride intake help to prevent dental caries. The control of drinking-water quality is therefore critical in preventing fluorosis. The condition and its effect on people Fluorosis is caused by excessive intake of fluoride. The dental effects of fluorosis develop much earlier than the skeletal effects in people exposed to large amounts of fluoride. Clinical dental fluorosis is characterized by staining and pitting of the teeth. In more severe cases all the enamel may be damaged. However, fluoride may not be the only cause of dental enamel defects. Enamel opacities similar to dental fluorosis are associated with other conditions, such as malnutrition with deficiency of vitamins D and A or a low protein-energy diet. Ingestion of fluoride after six years of age will not cause dental fluorosis. Chronic high-level exposure to fluoride can lead to skeletal fluorosis. In skeletal fluorosis, fluoride accumulates in the bone progressively over many years. The early symptoms of skeletal fluorosis, include stiffness and pain in the joints. In severe cases, the bone structure may change and ligaments may calcify, with resulting impairment of muscles and pain. Acute high-level exposure to fluoride causes immediate effects of abdominal pain, excessive saliva, nausea and vomiting. Seizures and muscle spasms may also occur. The cause Acute high-level exposure to fluoride is rare and usually due to accidental contamination of drinking-water or due to fire fires or explosions. Moderate-level chronic exposure (above 1.5 mg/litre of water – the WHO guideline value for fluoride in water) is more common. People affected by fluorosis are often exposed to multiple sources of fluoride, such as in food, water, air (due to gaseous industrial waste), and excessive use of toothpaste. However, drinking water is typically the most significant source. A person’s diet, general state of health as well as the body’s ability to dispose of fluoride all affect how the exposure to fluoride manifests itself. Distribution Fluoride in water is mostly of geological origin. Waters with high levels of fluoride content are mostly found at the foot of high mountains and in areas where the sea has made geological deposits. Known fluoride belts on land include: one that stretches from Syria through Jordan, Egypt, Libya, Algeria, Sudan and Kenya, and another that stretches from Turkey through Iraq, Iran, Afghanistan, India, northern Thailand and China. There are similar belts in the Americas and Japan. In these areas fluorosis has been reported. Scope of the Problem The prevalence of dental and skeletal fluorosis is not entirely clear. It is believed that fluorosis affects millions of people around the world, but as regards dental fluorosis the very mild or mild forms are the most frequent. Interventions Removal of excessive fluoride from drinking-water is difficult and expensive. The preferred option is to find a supply of safe drinking-water with safe fluoride levels. Where access to safe water is already limited, de-fluoridation may be the only solution. Methods include: use of bone charcoal, contact precipitation, use of Nalgonda or activated alumina (Nalgonda is called after the town in South India, near Hyderabad, where the aluminium sulfate-based defluoridation was first set up at a water works level). Since all methods produce a sludge with very high concentration of fluoride that has to be disposed of, only water for drinking and cooking purposes should be treated, particularly in the developing countries. Health education regarding appropriate use of fluorides. Mothers in affected areas should be encouraged to breastfeed since breast milk is usually low in fluoride. References World Health Organization. Guidelines for drinking-water quality. Vol. 1. Geneva, 1993 (Second edition) World Health Organization. Guidelines for drinking-water quality. Vol. 2. Geneva, 1999 (Second edition) Fluoride in drinking-water, WHO/IWA (in preparation) Prepared for World Water Day 2001. Reviewed by staff and experts from Oral Health Programme (ORH), and Water, Sanitation and Health Programme (WSH), World Health Organization (WHO), Geneva.
It would be interesting if all the critics of this Cochrane fluoridation review, who are painstakingly dissecting individual studies, would tell us why the first fluoridation human trials are scientifically valid. It was a time when virtually the only fluoride source was the water and each fluoridated community had a similar control non-fluoridated city e.g. Kingston/Newburgh; Grand Rapids, Muskegon, etc. These trials are the basis upon which fluoridation is promoted, supplements are prescribed and possibly fluoridated toothpaste was sold to the public. They don’t seem valid to me; but maybe you guys know better?
- Bill Osmunson DDS, MPH on 07/18/2015 at 00:27 said:
Although we may disagree, the Cochrane reviewers need to be thanked for once again reviewing the literature on efficacy of fluoridation.
Any review of fluoride ingestion should look both at the big picture and each research study.
For example, judgment should not be based on relative percentages which can be highly biased, but absolute percentages. Of 128 tooth surfaces, a reduction from 128 to 127 surfaces is less than one percent. However, a reduction from 2 of those 128 surfaces to 1 surface is a 50% reduction, in relative terms and less than 1% in absolute terms. Fluoridation may reduce dental caries by 0.6 surfaces which is not significant in absolute terms.
Numerous other problems to fluoridation efficacy include: Not one Randomized Controlled Trial Socioeconomic status often not controlled Inadequate size Difficulty in diagnosing decay Delay in tooth eruption Diet: Vitamin D, calcium, strontium, sugar, variables. Lack of total exposure of Fluoride with measured blood and/or urine fluoride concentration Oral hygiene habits Not evaluating life time benefit Estimating or assuming subject actually drinks the fluoridated water. Dental treatment expenses Breast feeding and infant formula Fraud or gross errors. Genetics and Dental office visits Cochrane suggests Prospective Randomized Controlled Trials of artificial fluoridation cannot be done, but quality studies can and must be done. Excuses are not results. After all, man has gone to the moon, we are looking close at Pluto, and certainly quality studies on fluoridation are possible. Remote communities could have water trucked to them.
Of course we would need to keep track of individual serum and urine fluoride concentrations, estimated exposure, etc. Singh (2014) (Singh N. et al A comparative study of fluoride ingestion levels, serum thyroid hormone & TSH level derangements, dental fluorosis status among school children from endemic and non-endemic fluorosis areas. Springerplus. 2014 Jan 3;3:7) is a good example of measured fluoride concentrations. The study is online and free, read it. Dental fluorosis is a poor and limited measurement of excess fluoride exposure. Singh had 3 groups of children, Group 1A with dental fluorosis, 1B without fluorosis (higher fluoride concentrations in water) and Group 2 drinking water at 1 ppm. Yes, 57% of those children with fluorosis had delayed eruption, but 50% without dental fluorosis also had delayed eruption. Delayed eruption alone could account for the minor reduction in dental caries reported by the Cochrane review. And the difference in Thyroid derangement between Group 1A and 1B was 77% vs 67%. OK, slightly less Thyroid derangement without dental fluorosis, but 2/3rds of those without dental fluorosis still have thyroid derangement. That is huge. And even those with 1 ppm, 50% had abnormal serum fluoride levels and 10% with thyroid derangement. Even gets more concerning when we consider the fluoride concentration of children in the USA due to other sources of fluoride.
Cochrane must demand actual measured evidence and if quality studies are not available, be more robust in candor. For example, what is the optimal tooth fluoride concentration? No one knows because both caries teeth and caries free teeth have the same fluoride concentrations. What is the optimal serum fluoride concentration to achieve the unknown tooth fluoride concentration? No one knows. What is the optimal total exposure of fluoride for dental caries reduction? No one knows. Yet some would suggest they know optimal fluoride concentration for water based on incomplete and low quality research. And they are so confident they take away everyone’s freedom of choice.
CDC says fluoridation is the best method of delivery, as long as freedom of choice is ignored.
Cochrane now needs to put the entire fluoride theory to the test. Be inclusive not only of alleged benefit, but also alleged risks. Then use judgment to determine whether the policy has more benefit than risk.
Problems with the word “bias” I am pleased this post acknowledges that the word “bias” may be misunderstood. However, I do not believe details “in the methods section and appropriate references” properly deals with the problem. Misinterpretations and distortions are being substantiated by cherry picked quotes from the Abstract and Plain Language Summary. And, unfortunately, these will be the only sections read by reporters and policy makers – and most probably will not get that far. Surely the authors have a responsibility to word their abstracts and summary in a fashion to limit such misinterpretation – and dishonest use by campaigners. Surely these sections could note what is actually meant by the word “bias” – perhaps even avoid the word all together and refer to confounders, etc., – together with noting that realistically one cannot expect such studies to satisfy the criteria used to judge clinical drug trials. I also believe the term “Confidence in the results” is inappropriate and liable to misinterpretation. It is also being cherry picked by anti-fluoride campaigners to misrepresent and distort the review’s findings. The “Truth” argument I do not accept the justifying arguments about “truth.” The claim “truth does not make allowances for studies that are practically difficult to conduct” seems to me disingenuous considering the nature of the review and its real-world target audience. Science is not about discovering the absolute truth – just as reasonable an approximation to it that is possible given technological, intellectual and other practical considerations. We do not judge studies in the exact sciences as delivering the absolute truth – we are well aware of the effect of such limitations even there. Researchers have a responsibility in their work to do the best they can to obtain a reasonable reflection of the absolute “truth” – given existing limitations in technology, theoretical understanding, previous research and funding available. Reviewers have a responsibility to realistically appraise the literature, attempt to objectively summarise it (being clear and realistic about their selection and quality judgement criteria) and to convey their findings and conclusions in a way that is understood by their main audience. They do not help their audience by conveying inappropriate information related more to their concern with absolute “truth” (that is impossible to achieve) than with delivering an easily understood summary of the current state of knowledge appropriate for this audience. What can we define as “truth” in the dental caries area anyway as fluoridation efficacy depends of many factors in the specific situation? We might say that the current understanding of chemical mechanisms underlying the protective action of fluoride at the tooth surface is pretty close to the “truth.” But when it comes to the real world where such reactions are just one component of the many factors influencing caries formation it is not possible to define a “truth” about community water fluoridation in terms of a precise percentage increase in caries free teeth, etc. Given that in any real world situation one has to consider a range of factors like socioeconomic problems, availability of effective dental health care, the provision of dental health schemes (some of which may contain regular fluoride varnish treatments), local diet, etc., etc., policy makers and health practitioners are not interested in a precise figure that an academic might consider the ultimate “truth.” They want to know if research shows CWF to be effective and what other factors they have to take into account when considering it is used in their specific circumstances. Word limitations of abstract and summary I don’t buy the argument of word limits preventing all relevant qualifications in the Abstract and Plain language Summary. The current wording is actually very wordy considering that separate paragraphs are used to indicate that no information was considered for several factors. It seems to me something like this would be shorter and more correct. Under Abstract – main Results. Remove this passage: “The majority of studies (71%) were conducted prior to 1975 and the widespread introduction of the use of fluoride toothpaste. There is insufficient information to determine whether initiation of a water fluoridation programme results in a change in disparities in caries across socioeconomic status (SES) levels. There is insufficient information to determine the effect of stopping water fluoridation programmes on caries levels. No studies that aimed to determine the effectiveness of water fluoridation for preventing caries in adults met the review’s inclusion criteria.” Replace with this shorter passage: “The majority of the selected studies (71%) were conducted prior to 1975. Most recent studies were cross-sectional and therefore not considered. Consequently no conclusion could be drawn about the widespread use of fluoridated toothpaste on the effects of water fluoridation. Selection limitations also prevented any conclusions about the effects of socio-economic differences, stopping water fluoridation or preventing caries in adult. Similar changes in other parts of the Abstract and Plain Language summary would, I believe, make the review more approachable. More importantly it would make it harder for ideologically-driven campaigners to cherry pick the review so as to misrepresent it and distort its findings.
- Bill Osmunson DDS, MPH on 07/20/2015 at 05:59 said:
Ken, I was mostly in agreement with your post until you got to the point where you (in effect) suggest the term “insufficient information” be removed because it would make the report more “approachable.”
When I put on my “Public Health Hat” I hear you (as I am) are uncomfortable with the policy of mass medication of everyone against their will, based on “insufficient information.” You appear to want more certainty in the Cochrane conclusion regardless of the evidence.
You have requested their sentence, ““The majority of studies (71%) were conducted prior to 1975 and the widespread introduction of the use of fluoride toothpaste.” be replaced with, “The majority of the selected studies (71%) were conducted prior to 1975. Most recent studies were cross-sectional and therefore not considered. Consequently no conclusion could be drawn about the widespread use of fluoridated toothpaste on the effects of water fluoridation.”
I believe Cochrane is talking about “total exposure” along with “topical use of toothpaste” and perhaps reduction of dental caries is the result of the confounding of toothpaste and maybe not fluoridation.
I don’t think Cochrane is talking about the fluoridated toothpaste’s effects on water fluoridation. You probably agree the intent of toothpaste is to effect teeth, not water.
What about “insufficient evidence” is “unapproachable?” Is science only approachable if it fits within policy or a chosen belief system?
In 1975 the FDA CDER withdrew approval for ingested fluoride supplements because the evidence of efficacy was “incomplete.” 40 years later the Cochrane review found the evidence of efficacy “insufficient.”
Quality scientific reviews of fluoridation appear to be quite consistent, the evidence of efficacy is incomplete, insufficient, does not support policy.
Randomized controlled trials can be done and until they are done, individual freedom of choice must be respected.
This Cochrane review had no scientific basis to throw bones to the CDC suggesting a percentage of efficacy when the evidence is “insufficient.” A percentage of efficacy cannot ethically be put on “insufficient” evidence. Such a concept is scientifically absurd. OK, the report was talking about 5 year olds, but when confounding factors, even just sealants, are included, the evidence is incomplete and insufficient for all ages.
Who paid, funded, provided the money for this review? Is Cochrane in the pocket of the CDC/ADA?
The risks of ingested fluoride outweigh the alleged benefit. For a non-lethal, non-contagious disease caused primarily by bad diet and poor hygiene, people should have the freedom to choose whether to ingest a highly toxic substance regardless of the “truth,” sufficient, insufficient, complete or incomplete evidence. After all, if a person wants to swallow fluoride they can swallow a pea size of toothpaste.
What about freedom is so hard to swallow?
Bill, it would be inappropriate to debate the fluoridation issue with you here. There are plenty of other places for that and I think the discussion here should be directed towards the Cochrane fluoridation review. I am not avoiding the discussion you appear to want – just suggesting it occur in a more appropriate place. You know where to find me.
Relevant to the discussion here though is your objection to my criticism of the use of the unqualified term “insufficient information.” Let’s be clear – my objection is to the lack of qualification, to the reason the information considered is insufficient. That is what is being exploited by anti-fluoride campaigners who are misrepresenting the review and its findings.
I merely want readers to be aware that the limitations of the selection criteria is responsible for the lack of information the review comments on. Surely it is no crime to ask communicators to make there messages more accurate and approachable.
No, I am not wanting the authors to present a certainty they do not have – just that they be clear about their specific reasons for lack of certainty.
Your comments about randomised controlled trials should be direct to the authors. As you disagree with their assertion such trials are not really possible with a social health policy like community water fluoridation (which is of course backed up by the fact that no such studies are reported) I suggest you will need to are your case with some detailed arguments. Personally I am happy about what the review says on this – I just ask that such qualifications should be made clear in the Abstract and Plain Language Summary.