There have been suggestions that the “decreases” in dental caries reported from fluoridation trials may be merely a statistical artefact due to a delay in the onset of the caries process.
This question was considered in 1980 in the present author’s book Fluoridation: Scientific Criticisms and Fluoride Dangers. It cited the studies by Dr Robert Weaver in 1944 and 1948 in North Shields and the “naturally fluoridated” South Shields. He said in 1948:
“I think that the most important lesson to be learned from the North and South Shields investigation is that the caries-inhibitory property of fluorine seems to be of rather short duration.” He concluded: “…there is in fact no very striking difference in the incidence of caries in the two towns.”
A professional statistician, K.K. Paluev, reported in 1957 that there had been a similar delay in the rates published after ten years in the reports from the two fluoridation trial cities of Grand Rapids and Newburgh.
In 1978 Professor Arvid Carlsson illustrated the results obtained by Forsman, who in 1974 surveyed the caries rates in two towns in Sweden which had 1.2 and 0.2 ppm fluoride in their water supplies. Professor Carlsson stated:
“The difference is so small that it corresponds to a retardation of the caries progress by about 1 year. The possibility that the difference is only apparent cannot be excluded, since it is well known that the effect of fluoride is to retard the diagnosis of caries lesions.”
The Royal College of Physicians stated in 1976 that in the U.K. studies by the Department of Health, in the age group 8 to 11 years: “…it appears that fluoridation merely postpones caries by about 0.8 cavities a year.”
In their paper entitled “The failure of fluoridation in the United Kingdom”, when discussing the final report of that U.K. Health Department study, Professor A. Schatz and Dr J.J. Martin stated in 1972:
“It is thus clear that fluoridation does not prevent or reduce tooth decay. Instead, it merely postpones the appearance of caries by about 1.2 years Fluoridated children develop the same amount of tooth decay as their non fluoridated counterparts The only difference is that caries starts developing approximately 1.2 years later in the fluoridated group.”
This delay, at least partly, could be due to the teeth of children in fluoridated areas erupting (breaking through the gums) at a slightly older age, and therefore being exposed to decay-producing factors for a shorter period.
Although the number of erupted teeth at each age was not stated in any of the four main trials, in the Newburgh one it was possible to calculate from the published data that the number of erupted teeth was less than expected. The data published from the Evanston study suggested that there had been a progressive decline in the number of erupted first permanent molar teeth in six-year-old children in Evanston between the commencement of the study in 1946 and 1951. Unfortunately, this trend could not be studied because, after that time, the authors ceased publishing the data they obtained for the first permanent molars.
Drs R. Feltman and G. Kosel (1961) over a period of fourteen years fed fluoride tablets to children “through their eighth year of life” and reported that there was: “… a delay in the eruption of the teeth in some cases by as much as a year from the accepted eruption dates.”
Dr J.W. Benfield remarked that three years after New York was fluoridated it became apparent that delays of two to three years in eruption time were common, and that there appeared to be an increase in the need for orthodontic treatment. However those clinical impressions were not written up into a formal study. The physiological basis for this delay in eruption was mentioned in discussing the hypothesis, that fluoridation increases orthodontic problems (Sutton, 1988a).
Unfortunately this extremely important question still has not been resolved because the published data are so scarce. It is remarkable that in the British official experiments no count appears to have been made of the number of teeth erupted, or if it was, the data have never been published
In 1960 Lord Douglas of Barloch referred to the possible delay in the eruption of teeth, and stated: “If this is so, it is a matter of grave concern for it indicates a profound physiological change.”
In a dental examination it is standard practice to record, for each person, the teeth which are decayed, filled or missing due to having been extracted or shed, and those which have not yet erupted. Therefore it is a very simple matter to determine, for each sex group, the average number of each type of tooth, and the total number of teeth, which have erupted at each age. However, even as recently as 1979, Whittle and Downer, published a report in the British Dental Journal on a fluoridation study in Birmingham, U.K., which failed to mention this vital subject. Both of these workers, although government employees, had post- graduate degrees in science.
However, the obvious importance of this factor was recognized by a general dental practitioner who made the examinations in a small-scale survey in the town of Bacchus Marsh, Victoria, in the “baseline examination” in 1963 (fluoridation had commenced in 1962). He recorded the number of erupted teeth in the 322 children (aged 5,8,11 and 14 years) who drank fluoridated water in the town. (Wood, 1975)
The fact that practically no reports on fluoridation trials state these obviously-available data, shows that the authors either did not realize the importance of this factor, despite its mention on numerous occasions in the dental literature, or that they intentionally suppressed the results.
In 1963, Conner and Harwood stated that in their study in Brandon, Canada: “A record was kept of all erupted permanent teeth”, but they did not publish their findings.
The suggestion has been made repeatedly that fluoride inhibits thyroid function, which in turn delays the eruption of teeth (e.g. Baume and Becks, 1954) In 1979, Drs L. Krook and G.A. Maylin described a mechanism which could have produced the considerable delay in the eruption of the teeth, of between 1.5 and 3.0 years, which occurred in cattle which were crippled with fluorosis (fluoride damage to bone) due to having been exposed to atmospheric fluoride pollution. They found that exposure to fluoride had produced a great decrease in the number of certain cells in bone (resorbing osteocytes) which play a major role in the resorption of the roots of the deciduous (first) teeth and of bone, both of which processes are necessary before permanent teeth can erupt normally.
“The delay in the eruption of the permanent teeth has also been reported in children in fluoridated communities.”
“The cause of the delay in eruption was shown in the present material. Fluoride arrests resorption of deciduous tooth roots and of the supporting bone. By inducing one disease [fluorosis], delays the manifestations of another [dental caries].” [Emphasis added]
One more factor which could produce what appears to be a delay in the onset of caries is unconscious bias in favour of fluoridation if the examiners have already formed the opinion that fluoridation reduces caries. Such a bias could affect their assessment when they are determining whether very early caries is present — a matter for their personal judgement and opinion.
That is, there could be, delay, not in the development of caries but in its recognition and recording in children in the fluoridated areas (and possibly the exaggeration of the caries score in nonfluoridated ones) Either or both of those processes would produce the illusion that dental caries had been delayed in the fluoridated cities.
This failure to avoid bias is a major deficiency in fluoridation trials and, to the scientist, the fact that observations were not made “blind’ must make suspect all the results reported from such a trial, Particularly as the dental examination of each child was made by only one examiner and there is no way of checking the results of the examinations.
A similarly biased result is obtained when the examiners are directed, after the commencement of the study. to alter their criteria for recording the presence of caries. so that the number of carious cavities filled is reduced. This occurred in the fluoridation trial in Hastings. New Zealand. After the initial examination, the dental “nurses” (who examine and fill the teeth of school children) were told by the experimenter who was conducting the trial, T.G. Ludwig, to alter their criteria for determining whether a tooth should be filled.
As a result of this change, in the fluoridated children, they filled only about a quarter of the very small carious cavities which they would have done using their former examination criteria (Colquhoun and Mann, 1986).
This change greatly reduced the number of filled teeth in the fluoridated test area. As the examiner carried out his examination soon after the children’s dental treatment was completed, it was not necessary for him to examine for decayed teeth. His task when examining the fluoridated Hastings children was the straightforward one of totalling the small number of missing teeth and those which had been filled which, due to his instructions to the dental “nurses”, was much smaller than it would have been if they had filled the teeth judged to be carious using their former criteria, which were still in use everywhere else in New Zealand.
These changes in the criteria for assessing the presence of caries were not mentioned by the author in any of his reports on his trial, they were revealed by Colquhoun and Mann (1986), who found out about these instructions by using the provisions of the freedom of information legislation.