by Paul Connett
We invite readers to compare figures 6. 1 and 6. 2. Figure 6. 2 appeared (as figure 1) in the CDC report that backed up its claim that fluoridation is one of the “Ten Great Public Health Achievements” in the twentieth century. 7 In this figure, the CDC authors show the decline in tooth decay in twelve-year-olds in the United States from 1967 to 1992. 9 On the same graph the CDC authors show the percentage of the American public drinking fluoridated water increasing over the same period. The suggestion is that tooth decay has come down in the United States during this period because the number of people drinking fluoridated water has gone up. In the text the CDC authors refer to this figure in the following context: “The effectiveness of community water fluoridation in preventing dental caries prompted rapid adoption of this public health measure in cities throughout the United States. As a result, dental caries declined precipitously during the second half of the 20th century. For example, the mean DMFT among persons aged 12 years in the United States declined 68%, from 4. 0 in 1996–70. . . to 1. 3 in 1988–1994. ”10
Decay Trends (in 12-Year-Olds):
Fluoridated vs. Non-fluoridated Countries
Figure 6. 1. Tooth decay trends in twelve-year-olds in fluoridated vs. a representative sample of non-fluoridated countries. Graph based upon plots by Chris Neurath. 8 Source: World Health Organization, 2004.
The problem with both the CDC’s statement and its figure 1 (reproduced in figure 6. 2) is that this agency is stating or implying a cause-and-effect relationship between increased use of fluoridation and the observed drop in tooth decay in twelve-year-olds. If the CDC authors had checked the WHO data for themselves, they would have been hard put to maintain that falling tooth decay in twelve-year-olds in the United States was simply due to the increased use of fluoridated water, as the same or greater declines have been achieved over the same time period in countries whose populations have not been drinking fluoridated water.
Figure 6. 2. Percentage of the U. S. population in areas with fluoridated community water systems and mean number of decayed, missing (because of caries), or filled permanent teeth (DMFT) among children aged twelve years in the United States, 1967–1992. Source: Figure 1 in CDC (1999). 11
Journalists and officials around the world are innocently using the CDC statement that “fluoridation is one of the top public health achievements of the twentieth century” without realizing how weak the CDC’s evidence for the benefits of this practice actually is.
Fluoridation vs. Income Level
One of the biggest factors that mars many studies claiming to show a benefit from fluoridated water is the failure to control for key confounding variables, and one of the most important of these is income level.
Dr. Bill Osmunson, a practicing dentist who supported fluoridation for twenty-five years before he began to research the issue for himself, has shown that, according to the results of a questionnaire administered to parents in all fifty states by the Department of Health and Human Services (DHHS), 12 there is absolutely no correlation between the percentage of parents who responded that their children had very good or excellent teeth and the percentage of the population in the state drinking fluoridated water. However, there is a very strong relation in all fifty states between the percentage of parents giving that answer and their income levels. Across the board, 80 percent of high-income parents gave that answer, but only about 60 percent of low-income parents did so (see figure 6. 3). 13
In 2002–2004 a survey of tooth decay in third graders in New York State was conducted by the pro-fluoridation New York Department of Health. 14 When Michael Connett plotted the tooth decay in New York third graders (averaged by county) against the percentage of the population of each county drinking fluoridated water, no relationship was found. 15 There was again, however, a relationship with average county income levels, though the relationship was less clear than that in the Osmunson data (see figures 6. 4 and 6. 5).
Other Variables
Figures 6. 3–6. 5 show that when comparing U. S. states or New York counties, income level is a far greater factor affecting dental decay than the percentage of the population that has fluoridated water. If this and other key variables are not carefully controlled and two towns are selected from a long list of towns (or counties or states), you can get any result you want.
Readers might not believe that promoters of fluoridation could apply such a crude means of influencing the public in these matters, but this appears to have been attempted in the case of the New York State survey. Before the study was published, figures for just two counties were leaked to a Syracuse, New York, newspaper. 21 Those figures purported to show that tooth decay in third graders was less in fluoridated Onondaga County than in non-fluoridated Cayuga County. However, as discussed above, the study did not take into account the key issue of income level or any other confounding variables. In 2008, Onondaga County had a median income level of $50, 586 compared to a median income level of $47, 308 for Cayuga County. Moreover, Onondaga County contains the large city of Syracuse whereas Cayuga County has only small towns. Larger cities tend to have more dental services than small towns and rural areas. A front-page article featuring this selective piece of information led to a push to fluoridate Cayuga County. Fortunately, the effort failed.
Figure 6. 3. Percentage of parents (of both high and low income) who responded that their child had very good or excellent teeth compared with the percentage of the population with access to fluoridated public water in each state and the District of Columbia. Source: Osmunson. 16
In the UK, promoters routinely contrast fluoridated Birmingham with non-fluoridated Manchester, with little more justification than that the two cities are comparable in size. Again, no careful account is taken of factors such as income level, ethnicity, educational level, and availability of dental services.
Non-Fluoridated vs. Fluoridated Countries
Since 1980, a number of prominent review articles and studies have found little or no significant difference in the level of tooth decay (especially of the permanent teeth) when comparing children living in fluoridated and non-fluoridated communities. These studies also are reviewed in chapter 8.
Figure 6. 4. Percentage of third graders with caries (average by New York county) plotted against the percentage of the population that has fluoridated water in each county. The line drawn on the figure represents the best straight-line fit to the data, resulting from linear-regression analysis. A horizontal linear regression line means that there is no apparent statistical relationship between the two variables plotted (in this case percentage caries rate in third graders averaged by county and percentage of the population in each county with access to fluoridated water). Source: Figure prepared by Michael Connett for the Fluoride Action Network based on NYDOH data. 17, 18
Figure 6. 5. Percentage of third graders with caries (averaged by New York county) plotted against average personal per capita income in each county. The line drawn on the figure represents the best straight-line fit to the data, resulting from linear-regression analysis. The fact that this line is sloping downwards from left to right suggests that as average per capita income for each county goes up the percentage of third graders with caries goes down. Source: Figure prepared by Michael Connett for the Fluoride Action Network based on NYDOH data. 19, 20
Figure 6. 6. Tooth decay in five-year-olds in New Zealand plotted over the time period 1930–1990. The plot also shows the periods in which fluoridated water and fluoridated toothpaste were introduced. 22
In chapter 5, we referred to four modern studies that showed that when fluoridation was halted in communities in British Columbia (Canada), Cuba, Finland, and the former East Germany, tooth decay rates did not go up as anticipated and in some cases continued to go down. The ADA claims that that was because the communities in question took other steps to reduce tooth decay commensurate with the cessation of fluoridation. 23 Some studies have even found that tooth decay rates increase as the fluoride concentration in the water increases. 24
–31
In New Zealand one of the unique features of the dental data collected is that under the country’s national health system, dental decay is measured in every five-year-old and every twelve-year-old. When John Colquhoun examined the historical data, he found that tooth decay rates in five-year-olds (1930–1990) were coming down long before fluoridation of the water began or fluoridated toothpaste was introduced (see figure 6. 6).
Maximization of Fluoride Benefit
Mark Diesendorf, in his article “The Mystery of Declining Tooth Decay, ” published in Nature in 1986, showed that the rate of tooth decay was coming down before fluoridation was introduced in communities in Australia and continued to decline after any benefits of fluoride would have been maximized (see figure 6. 7).
Figure 6. 7. Decline in caries, measured by DMFT, in Tamworth, Australia, for children in age groups six to thirteen years. The vertical line cutting the graph line for each age group denotes the year when the maximum possible benefit from fluoridation was reached. Tamworth was fluoridated in 1963. Source: Figure adapted from figure 1 in Diesendorf, 1986. 32
This finding remains relevant—but often overlooked—today. For example, after twelve years of a fluoridation program, any drop in tooth decay prevalence in future generations of twelve-year-olds cannot be ascribed to fluoridation. After twelve years of the program, all subsequent generations of twelve-year-olds will have been exposed to fluoridation for their whole lives. Further declines in tooth decay can only be explained by other causes. Today, careless observers credit all further declines in successive generations to fluoridation, even after the year in which any benefit would have been maximized for each age group (shown by the short vertical lines in figure 6. 7).
Factors Concealing a Lack of Benefit
A number of factors can cause an apparent or real decline in tooth decay that has nothing to do with the action of fluoride on the tooth itself. We discuss a few of these here:
• Delayed eruption of teeth. Until recently, few studies purporting to demonstrate fluoridation’s effectiveness have controlled for a possible delayed eruption of teeth caused by fluoride, for which there is some, albeit inconsistent, evidence. 33, 34 Komárek et al. controlled for this factor and found that the apparent benefit of fluoride largely disappears. 35 We discuss the details of the Komárek article in chapter 8.
• Primary versus secondary dentition. Those promoting fluoridation usually use the data on primary dentition (baby teeth) rather than secondary dentition (permanent teeth). We argue that decay in the permanent teeth is more relevant, however, since those are the teeth we hope to retain for the rest of our lives. In a videotaped debate between Michael Lennon, chair of the British Fluoridation Society, and Paul Connett, director of the Fluoride Action Network, held on the Isle of Man, all the statistics Lennon cited were for primary teeth, whereas all the studies cited by Connett, showing little or no benefit of fluoride, were for secondary teeth. 36
• Other minerals in the water. Many of the early trials and subsequent studies have been lax about ensuring that there are comparable levels of other minerals in the water that can affect tooth decay (e. g. calcium, magnesium, strontium) in the study and control towns. The levels of minerals in local soils might also be a factor if they enrich local food supplies with key tooth-building minerals.
Baby-Bottle Tooth Decay
Even promoters of fluoridation have conceded that it cannot prevent baby-bottle tooth decay (BBTD, also called nursing-bottle caries), a distressing example of tooth decay in infants, which often leads to extractions under anesthesia. BBTD is caused by babies sucking on sugared water, fruit juice, or carbonated beverages for hours on end. 37–44 Promoters of fluoridation are being dishonest when they use pictures of BBTD to make their case.
Explaining the Universal Decline in Decay
The Purported Halo Effect
Some promoters of fluoridation have tried to rationalize the similar rates of tooth decay in fluoridated and non-fluoridated communities by claiming a halo effect. They suggest that children in non-fluoridated communities are getting fluoride from food and beverages imported from fluoridated communities. However, this explanation cannot possibly explain the similar declines in rates of tooth decay in fluoridated and non-fluoridated countries in Europe (see figure 6. 1), because the majority of those countries are unfluoridated; thus, there is little or no source of fluoridated beverages or foodstuffs moving into non-fluoridated countries from the fluoridated ones.
Wrong Mechanism of Benefit
A more likely explanation for the similar rates of tooth decay in fluoridated and non-fluoridated communities came in 1999 (and again in 2001) when the CDC, a longtime promoter of fluoridation, conceded that promoters had got the mechanism of fluoride’s action wrong for over fifty years. The CDC admitted that the major benefits of fluoride are topical, not systemic 45, 46 (see chapter 5).
Thus, if fluoride has played any role in reducing tooth decay, it is more likely because of the universal availability of fluoridated toothpaste (which delivers fluoride topically), than because of the number of people swallowing fluoridated water. Indeed, in systematic reviews (compare Marinho47 with McDonagh et al. 48 ), the evidence that fluoridated toothpaste reduces tooth decay in children and adolescents is stronger than the evidence that swallowing fluoridated water does so. See also the review by Eaton and Carlile. 49
High-Sugar Diets
Some opponents of water fluoridation reject even the topical benefits of fluoride. They argue that tooth decay is a result of poor diet: too much sugar and not enough minerals and vitamins. They point out that in industrialized countries where high-sugar diets are relatively common, there is a very strong correlation between poverty and tooth decay. Thus, as the standard of living increases, the incidence of tooth decay decreases. An increased standard of living allows parents more money to provide better diets (more fresh fruit and vegetables) and to pay for preventative dental care. Since World War II, we have also seen the introduction of vitamin D–fortified milk and, in some countries, school milk programs. In the United States this coincided with the introduction of fluoridation. Vitamin D, calcium, and phosphate are present in milk and are needed for the healthy development of both primary and secondary dentition. It is possible that the recent increases in tooth decay being reported in some fluoridated countries may reflect the fact that some children are drinking less milk and more soft drinks.
Antibiotics in Processed Food
Another possible explanation for the overall decline in tooth decay in industrialized countries was offered by New Zealand researcher Betty de Liefde. 50 She notes that there has been an increased consumption of processed foods containing antibiotics as preservative agents. Some of those antibiotics, she argues, would reduce the bacteria in the mouth that are responsible for converting sugars to acids, which attack the enamel and begin the decay process.
Summary
The benefits of water fluoridation have been greatly exaggerated. The early studies that served as the basis for initiating fluoridation were methodologically flawed (for further discussion, see chapter 7). Since those early studies, many studies have failed to control for confounding variables, particularly that of income level. For several decades caries rates have been declining at a comparable rate in both fluoridated and non-fluoridated countries. Together with supporting data of several kinds, this shows that factors other than fluoride ingestion have been at work. Conversely, the experience of many poor city areas has shown that fluoridation cannot compensate for the shortcomings of diet and dental care.
•
7 •
The Early Evidence Reexamined
Coauthored by Peter Meiers
A great deal of the conviction that fluoridation works has been derived from two sources: Dean, Arnold, and Elvove’s famous two-part, twenty-one-city study in 19421, 2 and the early fluoridation trials in the United States, Canada, and New Zealand. Despite the weaknesses of both the Dean study and the fluoridat
ion trials, those early studies are cited again and again to support the claim of the success of fluoridation. As Benjamin Nesin, director of the New York State Water Laboratories, stated in 1956, “It must be emphasized that the fluoridation hypothesis in its entirety rests on a very narrow base of selected experimental information. It is this very base which is vulnerable to scientific criticism. And it is upon this very narrow base that the impressive array of endorsement rests like an inverted pyramid. ”3
In actual fact, that “impressive array of endorsements” began in 1950, long before these trials, which began in 1945, were completed in 1955. Proponents really didn’t need to have very much data available once the U. S. Public Health Service (PHS) endorsed fluoridation in 1950, halfway through the trials (see chapter 9).
The Dean Study
In describing Dean’s early work, the Centers for Disease Control and Prevention (CDC) stated in 1999, “Dean compared the prevalence of fluorosis with data collected by others on dental caries prevalence among children in 26 states (as measured by DMFT) and noted a strong inverse relation. This cross-sectional relation was confirmed in a study of 21 cities in Colorado, Illinois, Indiana, and Ohio. ”4 This raises the question, if Dean had access to data from twenty-six states, why did he use data from only twenty-one cities from four states in this critical two-part report? Did he select the cities that best supported his hypothesis? Dean’s twenty-one-city plot is shown in figure 7. 1.
