Public water supply fluoridation (PWSF) has been a controversial issue for over six decades. The efficacy of PWSF in combatting tooth decay is in dispute. The existence of harmful side effects is hotly debated. On a more fundamental level, there are bitter arguments over whether PWSF amounts to compulsory medication, and, if so, whether this is justifiable.
Below, I will show why I think the prestigious organizations endorsing PWSF are on shaky ground. To start with, we need to look at how fluoridation is supposed to combat tooth decay and then consider the issue of transmission of this disease. A surprising aspect is that, even if fluoride treatment did cure dental caries, this would not necessarily inhibit the spread of the disease. I will also survey the evidence of harmful side effects of fluoridation.
According to a report  of the Fluoride Recommendations Work Group, an authoritative body that advocates PWSF, fluoridation combats tooth decay in two ways. Quoting directly:
Dental caries is an infectious, transmissible disease in which bacterial by-products (i.e., acids) dissolve the hard surfaces of teeth. Unchecked, the bacteria can penetrate the dissolved surface, attack the underlying dentin, and reach the soft pulp tissue. ...
Fluoride works to control early dental caries in several ways. Fluoride concentrated in plaque and saliva inhibits the demineralization of sound enamel and enhances the remineralization (i.e., recovery) of demineralized enamel. ...This improved structure is more acid resistant and contains more fluoride and less carbonate. Fluoride also inhibits dental caries by affecting the activity of cariogenic bacteria.... it inhibits the process by which cariogenic bacteria metabolize carbohydrates to produce acid and affects bacterial production of adhesive polysaccharides. Whether this reduced acid production reduces the cariogenicity of these bacteria in humans is unclear. ...
The laboratory and epidemiologic research that has led to the better understanding of how fluoride prevents dental caries indicates that fluoride's predominant effect is posteruptive and topical. ...
So fluoridation proponents claim that fluorides reduce tooth decay by repairing the damage caused by acids generated by certain bacteria (the principal villain being streptococcus mutans), and possibly by also reducing production of these acids. The oral environment is extremely complicated, including a great variety of bacteria and chemicals interacting in ways that are not fully understood. A key point is that, at the levels used for dental purposes, it does not appear that fluorides kill off the offending bacteria--note that bacteria killing is not claimed in the above quoted essay. I found one article  claiming that fluorides kill bacteria, but it does not cite any supporting research. A research article I found  states:
Although very high levels of fluoride (0.16-0.3 mol/L) will kill bacteria, there is little evidence that fluoride causes dramatic changes in the number of species found in plaque or their relative concentrations.Some claim that fluoridation causes bacteria to evolve into forms that do not attack teeth.
In my previous discussion of fluoridation, I said, "Tooth decay, on the other hand, while sometimes painful, even disabling, and occasionally expensive to remedy, is not contagious." Turns out that's not quite right.
This is a tricky question, and an important one. First, the bacteria causing tooth decay can be transmitted from person to person. It is accepted that mothers commonly transmit such bacteria to their children via kissing. Transmission can also occur thru such mechanisms as the common use of inadequately cleansed tableware and dishes. Therefore we can assume that a person with tooth decay can indeed pass on this blessing to others.
The interesting point is that, assuming fluoridation successfully combats tooth decay as stated by its proponents, it is also possible to "catch" tooth decay from someone who does not suffer from this disease! This could occur if the transmitter is someone who, tho free of tooth decay thanks to fluoridation, nevertheless has a mouth full of streptococcus mutans.
The justification for chlorinating public water supplies, and therefore virtually compelling people to drink chlorinated water, is that this process, by killing off bacteria in the water, substantially reduces public exposure to deadly diseases such as cholera. So, unlike fluoridation, which purports to treat a disease, chlorination prevents the onset of several diseases by eliminating infected water as a direct cause. It also thereby reduces the number of diseased people who can transmit disease by other means. The justification for chlorination is that nobody has a right to endanger other people by becoming infected with a highly contagious disease. But this argument (at least in its direct form) does not hold for fluoridation.
At best, it appears that PWSF would reduce tooth decay for those people who drink water from that supply. It would not significantly reduce the number of people infected with decay-causing bacteria. It would, therefore, not reduce the number of people who can transmit tooth decay to others. So, even if we think fluoridation is effective in reducing tooth decay among those who drink fluoridated water, forcing it on those who, for whatever reasons, do not want to be so treated, cannot be justified by the argument that this will prevent them from infecting others. There is, however, another, more indirect, argument.
Suppose that severe tooth decay makes people very vulnerable to some other disease X, which is life threatening and highly contagious. If the likelihood of this happening were significant, there would be a strong case for, in effect, compelling people to accept some effective treatment to prevent tooth decay. (This serious argument was pointed out to me by my friend Leonard Zimmerman.) In order for it to justify PWSF, several requirements must be met:
While, on the face of it, point-1 seems plausible, I have not been able to find an example of a type X disease. This, of course, does not mean that such does not exist, and I would appreciate information on this. There is great controversy over points-2 and 3.
There are a number of ways in which fluorides are administered in accordance with the notion that the topical effect is what counts. These include incorporation in tooth paste, mouth rinses, lozenges (to be chewed and/or sucked), gels and enamels. A number of states have programs in which school children (with parental consent) use fluoride rinses once a week. They swish the rinses in their mouths for about a minute, not swallowing, and then spit out. These alternatives all share the advantage over water supply fluoridation that the dosages are more easily controlled.
In addition, since only minimal amounts are ingested, the possibility of detrimental side effects is substantially reduced. A basic advantage is that nobody is compelled to imbibe fluorides (or else have to go to a lot of trouble and expense to obtain drinking water without it).
It is generally agreed that people exposed to drinking water fluoridated to an extent exceeding about four times what is considered the optimum level for combatting tooth decay (1 ppm, i.e., one part per million), run a significant risk of dental fluorosis. The symptoms of this disease range from mottling of the teeth, thru severe pitting, weakening, and, as a result, tooth loss. Depending on various factors, such as the amount of water consumed per day, presence of other substances in the water, age, and the condition of one's kidneys, dental fluorosis can occur at fluoride concentrations down to 1 ppm, or even lower. This is the only detrimental effect of fluoridation acknowledged by PWSF supporters. And many of them consider it, not a disease, but only a cosmetic effect.
But, altho careful large-scale studies have not been carried out, there are numerous published papers describing both laboratory research and epidemiological studies, that indicate, with various degrees of persuasiveness, that fluorides can cause or aggravate a variety of serious conditions including skeletal fluorosis, other bone diseases, kidney ailments, and various kinds of cancer . This should not be surprising given the poisonous nature of fluorides. The problem is further exacerbated by the fact that fluorides added to water supplies are derived from industrial wastes and there is evidence that they are contaminated with lead and other heavy metals .
In additional to scientists with impressive credentials, the opposition to fluoridation includes many people who are driven more by emotion than by knowledge. This has the effect of obscuring the issues. I believe fluoridation proponents have not dealt adequately with the arguments of serious opponents. Supporters rely heavily on epidemiological data. They seem to ignore the fact that tooth decay has been declining worldwide for many years, that this trend seems to be independent of the amount of fluoride present in water supplies, and that it seems to be unaffected by the introduction and growth in use of fluoridated tooth paste.
It is interesting that, in many other nations, including all the Nordic countries, Germany, Switzerland, and India, the attitude of both the population and established organizations is quite different. Water supplies in these countries are almost all not fluoridated, while the incidence of tooth decay is generally less than in the US .
My best guess, based on a perusal of the literature, is that naturally and artificially fluoridated water supplies have a small effect in reducing tooth decay, and that topical applications of fluorides have a somewhat greater, tho not great, effect. It appears likely that neither way of administering fluorides does much to reduce the population of decay-causing bacteria, and so do little, if anything, to prevent the spread of tooth decay.
Given that over half the population of the United States is involuntarily subjected to what amounts to a particular medication for their entire lives, it is not enough to say that there is no conclusive evidence that such treatment has harmful effects. It is appalling that there has been no systematic research program to justify a positive assertion that PWSF is harmless both in the short run and in the long run. From what I have read, I think it is likely that there are indeed serious harmful effects on substantial numbers of people.
Tooth decay is in the category of "Western" diseases, i.e., diseases associated with the life styles of modern civilization. People living under primitive conditions, e.g., in remote jungle areas, do not suffer from these diseases, which also include obesity, diabetes, heart disease, and cancer. The key factor in tooth decay seems to be sugar in the diet. I believe the best way to attack tooth decay successfully would be a serious educational program, starting in the schools, to impress on children and adults the need for simple measures such as brushing one's teeth at least twice daily, and not using one's mouth as a sugar reservoir. This would reduce tooth decay directly and would reduce the population of decay-causing bacteria, thereby reducing the transmission effect.
Finally, given the substantial uncertainty with respect both to the efficacy and safety of fluoride use, I think it is wrong to impose this medication on unwilling people.
Comments can be sent to me at unger(at)cs(dot)columbia(dot)edu
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