CHAPTER 10:
THE QUESTION OF DELAYED ONSET OF CARIES
There have been suggestions that the
"decreases" in dental caries reported from fluoridation trials may be
merely a statistical artifact 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. They stated:
"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]
Bias.
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.
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