Ch. 4 The Greatest Fraud Fluoridation: Errors and Omissions in
Experimental Trials - 1d THE BRANTFORD STUDIES [cont.] Delayed eruption or
"weighting"? by Philip R.N. Sutton from fluoridationfacts.com
Errors
and Omissions in Experimental Trials - 1d
THE
BRANTFORD STUDIES [cont.]
Delayed
eruption or "weighting"? These results could
have arisen by there being a delay in the eruption of these teeth in the
Newburgh children, for it is unlikely that the
eruption rate altered in the
Kingston subjects. However, Ast et al.,
(195 1) said that "there does not seem to be any change in the eruption
pattern among the children in Newburgh, the study city, as compared with those
in Kingston, the control city." No definition of an "erupted
tooth" was given, but it is presumed that the authors of this study did
not adopt the odd method used in Evanston, where "Only teeth which were 50
per cent or more erupted were considered. A carious or filled tooth was, of
course, considered regardless of its stage of eruption" (Hill et al., 1955).
The conclusion of Ast et al. that has just been mentioned was reached only four years
after the commencement of fluoridation, and as the teeth considered were
partially formed prior to the commencement of that process, they would not show
effects which the ingestion of fluoridated water may produce on the early
stages of tooth development.
If delay in eruption did not occur in
Newburgh, the lower number of permanent teeth present at those ages in that
city compared with that present in Kingston was due to a "weighting"
effect; there having been, in proportion, more young children in each of these
age groups in Newburgh than there were in Kingston. If this is the case, as it
is reasonable to assume that the mean DMF rates of the younger children were
lower than those of the older ones, it would appear that in these age groups
the contrast between the DMF rates in Newburgh and those in the control city
was exaggerated in the final report.
"Smoothing" of initial rates.
In 1951 Ast et al. reported that the "initial
clinical examinations made in Newburgh and Kingston in 1944-1946 were made by
one examiner, at which time the DMF rates were the same." However,
reference to Table 2 in that paper shows that the DMF rates per 100 erupted
permanent teeth were, in Newburgh and Kingston respectively, at age six years,
8.5, 7.2; age seven years 11.7, 12.0; age eight years 17.1, 17.3; age nine
years 21.2, 18.9; age ten years 21.9, 21.3; age eleven years 21.8, 21.8, and
age twelve years 25.3, 25.4. Also, Table 5. which shows the DF rates per 100
deciduous teeth present, gives the rates in Newburgh and Kingston respectively
as 27.2, 21.5 at age five years; 34.2, 32.1 at age six years; 42.3, 43.3 at age
seven years, and 48.0, 47.2 for the eight-year-old children. Data for the DF
rates of the deciduous teeth of older children were not provided.
In the first report of this study (Ast et al., 1950) no results were given for
the deciduous teeth, and the results for the permanent ones were presented in
three age groups, six to seven, eight to nine and ten to twelve years. It can
be seen that by adding the data from children aged six years, in whom the DMF
rate in Newburgh was higher than that in Kingston, to those of the
seven-year-old children, in whom the reverse situation was present, the
divergence between the rates prevalent in the two cities was reduced. In Table
I (Ast et al., 1950) the combined
rate was shown as 10.7 in Newburgh and 10.8 in Kingston. In a similar manner,
the addition of the data for eight and nine-year old children and those of
children who were ten, eleven and twelve years of age produced a levelling
effect between the rates of the two cities in these two combined age groups. This
process of combining data >from children of different ages, when reporting
the DMF rate per 100 erupted permanent teeth, although it was employed in only
the first and the last dental reports, may have been used in order to simplify
the presentation of the data; but it had the unfortunate effect of disguising
differences between the DMF rates in the two cities at the time of the basic
examinations. In the next report the situation was stated more accurately, Ast
and Chase (1953) saying that "the DMF rates in both cities were
approximately the same at the start of the study".
Fluctuations
in the control city. In this, as in other studies, it is
found that the comments made in the text tend to underrate the changes that
took place in the dental caries attack rates in the control city. In the
summary of the paper by Ast et al.
(195 1) it was stated that "the DMF rates in the control city of Kingston
show no changes." In that paper, Table 2 shows the DMF rates per 100
erupted permanent teeth; in Kingston the "per cent change" in the
rates of the four age categories six, seven, eight and nine years were 30.5,
7.5, 0.6 and 9.5 respectively. Small changes were shown for ages ten, eleven
and twelve years. It should be noted that the six, seven and eight-year-old children
all showed decreased rates between 1945-6 and 1949. No attempt was made to
explain these decreases, and the water of Kingston "remained fluoride
deficient throughout the study period" (Ast et al., 1956).
Fluctuations
disguised. The method used by Ast et al. in 1951 was to compute the mean DMF rate per 100 teeth in
all the children aged six to twelve years; the Kingston rate for this combined
age group declining slightly from 20.2 to 19.9 between 1945-6 and 1949.
However, by adjusting to the "permanent tooth population in Kingston
1945-6 examinations", the authors showed that the rate of 19.9 became
20.2. On this basis it could be claimed that the "rate" in Kingston
had not changed, but the incorrect statement was made that the DMF "rates"
in the control city of Kingston showed no "changes". These rates of
19.9 and 20.2 were produced by combining the data of young children - that had
few erupted permanent teeth and relatively low DMF rates per 100 teeth with
data of older children that had most of their teeth erupted, and considerably
higher DMF rates per 100 teeth. The rate obtained in 1949 was then adjusted.
This procedure, no doubt unintentionally, disguised the fluctuations in the
rates in the control city.
In Table 2 (Ast et al., 195 1) the "per cent change" in the Kingston
children aged nine years was shown as 9.5, but if the figures 18.9 and 19.1 are
the correct ones for the years 1945-46 and 1949, the "per cent
change" should have been stated as 1.1, not 9.5.
Variability
of caries rates. Unfortunately, the variability of even
the mean caries rates cannot be studied, for the rates of yearly age groups
were not published in the first and the last reports (Ast et al., 1950, 1956), and the only results shown in the 1955 report
of Ast et al. were based on a
combined clinical and X-ray examination.
The
meagre data supplied for deciduous teeth. Data
regarding the caries rates of the permanent teeth were shown in each report of
this study; however, only very meagre data were published for the deciduous ones.
None were made available in the first report (Ast et al., 1950). In the following year (Ast et al., 195 1) the DF rates per 100 deciduous teeth were given, but
only for children aged five, six, seven and eight years, and in each age group
the rates had decreased both in the test and in the control cities.
Unexplained
marked decreases in the control. No explanation was
given by Ast et al. (1951) for the
decreases in the DF rates in Kingston, where the greatest relative decrease,
from 32.1 per cent DF to 24.8 per cent DF, was seen in the teeth of the six
year-old children. It would have been of great interest to see whether this
trend was maintained in later years, but DF rates were not stated in the tables
contained in any of the later reports. However, in the following one (Ast and
Chase, 1953) the situation in regard to the deciduous teeth of children five,
six, seven and eight years old (now termed "def teeth per 100 deciduous
teeth present") was depicted diagrammatically by means of a histogram,
these unexplained decreases in the def rates in the control city being clearly
seen, a small one at age five years, and considerable ones at the ages of six,
seven and eight years.
The
increase in caries-free teeth in the control. The only other information published
regarding the deciduous teeth was expressed in terms of "Children with
caries free deciduous cuspids, first and second molars". This type of
table appeared first in the 1951 report of Ast et al., and the results were given for only those children who were
five or six years of age. In both age groups in Kingston the figures suggest an
increase in these caries free teeth, the six-year-old children changing,
between 1945-6 and 1949, from 17.2 per cent to 25.5 per cent free from caries.
These changes were mentioned, but no attempt was made to explain them. In the
next report (Ast and Chase, 1953) data for children aged seven years were also
included. This report showed that, between 1945-6 and 1951-2, the percentage of
children in Kingston who had these deciduous teeth free from caries showed a
slight decrease at age five years (28.2 per cent to 26.4 per cent); but in the
six-year old children the percentage increased from 17.2 to 26.3; and in those
who were seven years of age, it practically doubled (8.3 to 16.5). On this
occasion, these changes in the control city were not even mentioned.
"Analysis"
of findings. In the 1955 report of Ast et al. it was stated that "As an
indication of the benefits of water fluoridation to deciduous teeth, a previous
report [in 1953] analyzed the findings among the 6 to 7 year old children in
each city after six to seven years following the initiation of water
fluoridation." Actually the report showed findings for the children aged
five, six and seven years who had caries-free deciduous cuspids, first and
second deciduous molars. At the ages of six and seven years, in both the test
and the control cities, there were increases in the percentages of these teeth
that were free from caries; therefore, although these increases were greater in
Newburgh, they should not have been attributed solely to water fluoridation. In
any case, the publication of one table showing, in this selected group of
deciduous teeth, the percentage changes that have just been mentioned, a
histogram depicting the def rates, and twenty lines of comment in the text on
the results displayed, can hardly be said to indicate the benefits of
fluoridation to deciduous teeth, or even to constitute an adequate analysis of
the findings in regard to the deciduous teeth present in children aged six and
seven years.
Changes
in caries-free teeth in the control. In the 1955 report of Ast et al. the age range was changed by not
publishing the results for the five-year old children, but showing, for the
first time, the results for caries-free deciduous cuspids first and second
deciduous molars, for eight and nine-year old children. However, these results
cannot be compared with those of the previous years, as they were based on a
combined clinical and X-ray examination. Nevertheless, a comparison can be made
with the rates shown in the final report (Ast et al., 1956). In the year between the 1953-4 and 1954-5
examinations, the rates in Kingston for the ages six, seven, eight and nine
years changed from 10.6, 7.0, 7.9 and 0.0 to 11.1, 4.7, 1.8 and 1.6 for the
respective ages. Such changes are not unexpected, for marked variations were
seen in Evanston, where, also, the examinations were made by a clinical plus
X-ray procedure. For instance, the percentages of children aged seven years who
were drinking fluoridated water and who had caries free deciduous teeth were,
in successive examinations, 11.33 (pre-fluoridation), 8.71, 3.87, 10,66, 13.01
and 17.86 (Hill et al., 1956). It
would seem that assessments made on the basis of caries-free groups of
deciduous teeth are not very reliable.
Changes
in the sampling method. Consideration of these five dental
reports shows that the sampling method changed from time to time, and that the
method used in the control city was sometimes the same and sometimes different
from that used in the test one. In the first report (Ast et al., 1950) it was stated:
"we are considering only those children
age 6-12 who were in the original base study and who have had each successive
examination until they reach age 12. Also included are new school children who
entered the study at age 6 subsequent to the first examination and were present
at each of the successive examinations. Thus, this study group will have only
those children who we are assuming have had continuous residence in their
respective cities."
Continuous
residence only assumed. It can be seen that the
"continuous residence" of each subject was based on assumption only,
and not on statements made in a questionnaire, such as was used in Evanston
(Blayney and Tucker, 1948). Therefore, it is possible that children could have
been absent from the city for considerable periods between the times of
successive examinations. Also, there is no assurance that the six-year-old
children entering the study in any of the post-fluoridation examinations had
not come to live in the area since the commencement of the study. Therefore, it
is doubtful whether the objective of having "reasonable assurance that the
children studied had had continuous residence in their respective cities"
(Ast et al., 195 1) can be said to
have been attained.
Population
changes in Newburgh. "Early in 1950 questionnaires were
given to more than 3,200 children in the Newburgh schools for completion by
their parents" (Ast et al., 195
1). The questions asked were not stated, nor was the number of replies
received, but it was said that:
An analysis of the answers to those
questionnaires shows that the Newburgh population is a relatively stable one
and that the inclusion of the small migrant groups does not alter the caries
picture to any significant degree. Consequently, in this report there are
included all 5 to 12 year old children present in the schools in Newburgh and
Kingston on the days the examinations were made" (Ast et al., 195 1).
Since information in regard to the caries
attack rates in these migrant groups could not have been obtained directly from
the questionnaires, it is presumed that the dental record cards of those
children were grouped and that the cards of the children who were judged from
the answers not to be migrants were also grouped, and the data contained in the
two groups in regard to the caries attack rates were compared. If that process
was carried out, it was not mentioned, nor were data published which would
enable the reader to assess the situation. If no differences were found between
the two groups, it must be considered to be strange because by that time it was
said that "The DMF rates among permanent teeth of 6 to 12 year old
children in Newburgh show a consistent downward trend" (Ast et al., 195 1). The United Kingdom
Mission (1953) reported that the authors of this study had "found that the
proportion of immigrants in Newburgh and Kingston was too small to affect the
comparison." However, although the Newburgh population was said to be
"relatively stable", in the 1954-5 examinations in that city 24 per
cent of the children were excluded because they failed to fulfil the residence
qualifications (Ast et al., 1956).
The workers who conducted the paediatric
study in these cities, Schlesinger et al.,
in 1950 said that in each city "An effort was made to select... children
from families which might reasonably be expected to remain for the duration of
the study." In spite of that precaution, they found that 29.9 per cent of their
subjects in Newburgh moved from the city during the period of the study
(Schlesinger, Overton, Chase and Cantwell, 1956).
Population
movement in Kingston. No mention was made of the issue of a
questionnaire to children in the control city; apparently it was assumed that
migrants to that city would have come >from areas with
"fluoride-free" water supplies. Schlesinger et al. (1956) found that 22.2 per cent of the children included in
the paediatric examinations moved from Kingston during the period of the study;
presumably a similar number of new residents settled in the city.
It may be considered that in moving from one
locality to another, interruptions could occur to regular conservative and
prophylactic treatment of the children, so that their dental health may not
have been as good as that of children who lived for many years in the same
city. It is possible also that regular dental examinations, by stimulating
interest in the teeth, may improve eating habits and oral hygiene measures.
Considerable
alterations in populations.
In Table I of Ast et
al. (1950) the number of permanent teeth erupted is shown. The numbers
given for Newburgh in the examination of 1944-5 for the three age groups six to
seven, eight to nine and ten to twelve years are respectively 3,579, 7,937 and
24,586. However, by adding in Table I of Ast and Chase (1953), the number of
erupted teeth - for the same age groups, and in the same examination - are
5,379, 10,033 and 27,186. It was stated in the former report that "we are considering
only those children age 6-12 who were in the original base study and who have
had each successive examination until they reach age 12." It therefore
appears that to meet those requirements, it was necessary to exclude, for the
three age groups, 33 per cent, 21 per cent and 10 per cent of the number of
erupted teeth, and, presumably, similar percentages of children. A like
situation was seen in regard to the Kingston data, the percentages of teeth
excluded being 24, 26 and 12. After only four years, it was apparently
necessary to omit these large proportions of the data in order to consider only
those children who were "continuous residents", no other explanation
being evident for the different numbers of erupted teeth that were stated in
the two papers. Although the population of Newburgh may have been
"relatively stable" when compared with some unnamed population, it is
obvious that the number of migrants was so great that they should have been
excluded from the study.
Data
of migrants excluded only in Newburgh. The necessity for
excluding the data of migrants was later realized, and the method of including
in the study all the children present in the schools on the day of the
examination - although it was continued in Kingston - was abandoned in Newburgh.
Ast et al. (1955) stated: "Based
on residence histories, the Newburgh study group was limited to those who had
used Newburgh water since the introduction of sodium fluoride on May 2,
1945." In the final report, also, only those children who had lived continuously
in Newburgh were included, but "All the Kingston children examined are
included in this report" (Ast et al.,
1956).
Alterations
in sample size. The sample size and the age
distribution of the children were altered during the course of this study. The
data included in the first three dental reports were obtained from the
"entire elementary school populations" (Ast and Chase, 1953), except
that in some years some of the children were excluded in Newburgh on
residential grounds, and that in 1951-2, owing to the loss of an examiner, only
half of the children in each city were included. However, in the 1953-4 series
the age range was restricted to six to ten years, and the number of children
examined was only a small fraction of those inspected in the same age groups
during other examinations. Ast et al.
(1956) said that the preceding report "dealt with rather small groups of
children (about 375 children ages six to ten in each city), and there was
considerable difference in age distribution."
Sampling
by selection.
The method of sampling used in the 1953-4 examination
must be considered to be unorthodox, and was described by Ast et al. (1955) in these words:
"The current series includes a limited
number of schools which were chosen because of the availability of X-ray
facilities. From previous data on DMF rates by school, it was determined that
the selected Kingston school had a caries rate which was among the lowest in
the city, while the rates for the three Newburgh schools were distributed
through the range of rates for that city. This has the effect of minimizing the
difference in the DMF rates between the two cities."
A
decrease in the "per cent difference".
In the final report (Ast et al.,
1956, Table 1) the "per cent difference" between the DMF rate per 100
erupted teeth of children aged six to nine years in Newburgh and Kingston was
given as 56.7. This is a smaller difference than any of those shown for the
ages six, seven, eight and nine years (74.7, 68.3, 58.1 and 66.0 respectively),
in the previous (1955) report, despite the fact that it was stated in that
report, that the sampling method used had minimized the difference between the
DMF rates in the two cities. A trial period of ten to twelve years was
suggested by Ast (1943), and was mentioned in the authors' first report (Ast et al., 1950). In view of the decrease
in the "per cent difference" between the test and the control cities,
which was revealed in the final report, it is unfortunate that the trial was
stopped as soon as the minimum period proposed by the authors had elapsed.
DISCUSSION
The Expert Committee on Water Fluoridation of
the World Health Organization (1958) stated that "Hundreds of controlled
fluoridation programmes are now in operation in many countries. Some have been
in progress for the past 12 years, so that conclusions are based on
experience." This statement suggests that there is a large amount of
experimental evidence in regard to the process of artificial fluoridation. It
is very doubtful whether this is the case. If hundreds of fluoridation
programmes have been conducted with experimental controls, it is strange, and
very unfortunate. that such a large body of data has not been published; for,
except in the cases of the trials which have been considered here, published data
concerning fluoridation trials are very meagre. It would seem, therefore, that
the Expert Committee did not use the term "controlled" in its
experimental sense, but in that of regulated measurement of the fluoride salt,
such as in its statement that "The precision of fluoride application
should be carefully controlled."
The United Kingdom Mission (1953) which
visited North America in 1952, in its report referred to "the Fluoridation
Studies", and enumerated only six study centres; and Jenkins (1955) mentioned
"the six study centres on the American continent". In addition to the
four test cities which have been considered, the Mission referred to Sheboygan,
Wisconsin, and to Marshall, Texas. No control city for Sheboygan was mentioned;
and the Mission stated that in the latter study "The neighbouring town of
Jacksonville with a fluoride-free water supply was selected as control, but
although caries experience in the two areas was compared after 2 1/2 years of
fluoridation, the most valuable basis for comparison is the baseline data of
Marshall itself." The Mission quoted two unpublished reports as the source
of its information in regard to the latter study. An indication of the minor
importance of these two trials is the fact that in the 240-page report of the
New Zealand Commission of Inquiry (1957) no data from them were presented, the
former city being mentioned twice and the latter only once. Furthermore, the
directors of these studies, Doctors F A. Bull and E. Taylor, were not named in
the report, and the extensive bibliography did not include any papers published
by them.
The crucial importance, even at the present
time, of the trials conducted in Newburgh, Grand Rapids, Brantford and Evanston
was demonstraled by the report made in 1957 by the New Zealand Commission, the
hearings of which did not conclude until April of that year, and by the report
of the Expert Committee of the W.H.O. (1958), which met during August 1957. The
only evidence mentioned by the Commission with regard to the dental results of
the addition of fluorides to water supplies was that obtained in those four
cities. The Expert Committee referred to only the first three of those cities
in the few lines of its report which mentioned dental results of fluoridation.
In discussing the general design used in
fluoridation studies, the United Kingdom Mission (1953) said:
"In a fluoridation study, two nearby
towns, comparable in all respects, are chosen, both having an almost
fluoride-free domestic water supply, preferably from the same source. The water
of one town is fluoridated while that of the other remains untreated, this town
serving as the control. Before fluoridation is started the teeth of the
children in both towns are examined in detail to ascertain if caries experience
is similar and to determine its prevalence in the various age groups. Further
examinations are carried out at yearly intervals and the dental condition of
the children in the fluoridated town is compared with that of similar groups in
the control town. The prefluoridation data also serve as a basis for
comparison. The caries incidence may also be compared with that in a town where
a similar concentration of fluoride occurs in the water naturally. In practice
it is often difficult to obtain all these conditions and in some studies there
is no independent control."
The term "comparable in all
respects" describes a theoretical ideal for a test and a control town
rather than a practical possibility. In regard to the other matters mentioned
in the design these studies exhibited numerous deficiencies. No control was
employed in the City Council study in Brantford, and the Grand Rapids study
lost its control in 1951 as a result of the fluoridation of the Muskegon water
supply. In the extremely important matter of the water supplies, both the
source and the composition of the Newburgh water is considerably different from
that of Kingston. Further examinations were "carried out at yearly
intervals" only in Grand Rapids-Muskegon, and in Newburgh-Kingston until
1952; if yearly examinations were made in the latter study after that year, the
results for all years were not published. In the Evanston trial, only two
examinations were made in the control city, and few data from it have been
published; in the test city only one age group was examined each year. In
Brantford and in Evanston, and in the first and the last dental reports from
the Newburgh-Kingston study, data from children of different yearly ages were
added, thus introducing the possibility of "weighting". In some instances,
at least, the degree of "weighting" found indicated that the
comparisons were not being made between similar groups in the test and the
control cities. No pre-fluoridation data were gathered in Brantford by the
Canadian Department of National Health and Welfare, for that study was not
commenced until over two and a half years after the fluoridation of the city
water supply.
In all of the studies that have been
considered, it has been seen that fluoridation of the water supply of the test
city was initiated before the initial caries rates in the control city were
known. This late examination of the control cities, on first thought, may not
seem to be of much consequence. However, it means that, in all of these
studies, a matter of fundamental importance was disregarded-it could not have
been established that the children of similar ages in the test and the control
cities, prior to the commencement of the experiment, had reasonably comparable
caries attack rates. Therefore, the statement of the United Kingdom Mission
(1953) that "Before fluoridation is started the teeth of the children in
both towns are examined in detail to ascertain if caries experience is similar
and to determine its prevalence in the various age groups" appears to have
been based on assumptions only.
Caries attack rates may be expressed as
decayed, missing and filled teeth per 100 erupted teeth, or expressed as per
100 children or per child. The former method was preferred by the authors of
the Newburgh trial "because individual teeth may be subjected
independently to the hazard of caries" (Ast et al., 1956). In the Evanston study, the rate per 100 erupted
teeth was given, but, curiously, only for children aged twelve to fourteen
years. All other cases (the younger children in Evanston, and the other
studies) in which the caries attack rates per 100 children or per child were
given are based on the assumption, unsupported by published evidence, that in
each age group the mean numbers of each category of erupted teeth per 100
children is very similar in the test and the control cities, and that little
variation occurs from year to year. If this is not the case, comparisons
between the rates prevalent in the test and the control cities, and those seen
in different years, are not valid. Feltman (1956) gave fluorides in tablet form
td-pregnant women and young children, and reported that "Many children in
the study group showed a marked delay in the eruption of the deciduous teeth.
This delay is in some instances a cause for alarm by the parents. The second
incisor, second molars, and cuspids are the most frequently delayed, in many
cases by as much as a year from the accepted average eruption dates." Of
course, if fluoridation results in the eruption rate of teeth being retarded, a
decrease in caries experience would be expected due to the shorter time of
exposure of the teeth to the risk of caries. It will be recalled that data were
published in the Evanston study which were compatible with a continuous and
marked decline in the rate of eruption of first permanent molars during the
first four to five years of fluoridation, but that further comparisons could
not be made because this type of data was not published for younger children in
later reports.
In order to decrease the chance of
misinterpretation, extensive use has been made of direct quotation from the
original reports, and to avoid unnecessary repetition, consideration of the
comments made on the results reported from these control cities, apart from
those made by the authors of these studies, has been restricted to the
statements of only a few writers.
It is felt that it is not necessary to
discuss further the matters which have been noted above, for they are
self-explanatory. It has been shown that the reports of the controls used in
these fluoridation trials contain arithmetical and statistical errors, and that
results and relevant data were omitted. Also, misleading statements were made
which denied, ignored, or underrated the unexplained changes in caries attack
rates which took place in the control cities, and which suggested that the
pre-fluoridation data from the test cities, and those obtained during the basic
examinations in control ones, were more closely comparable than was the case.
Jean R. Forrest, the Senior Dental Officer, Ministry of Health, who was a
member of the United Kingdom Mission and of the Expert Committee on Water
Fluoridation of the World Health Organization, in 1957 contrasted "the
emotional type of opposition" to fluoridation, to "the precise
correct statements of scientists," However, the situation which has been
encountered is more aptly described by the words of Wade Hampton Frost "an
outstanding American epidemiologist" (Bews, 1951). More than thirty years
ago Frost (1925) said:
"It is frequently easy to exhibit some figures
which, though not really to the point, will nevertheless serve to impress an
uncritical public, and the temptation may be great to give them, at least by
implication, an unduly favourable interpretation. It is more difficult and more
tedious to present the full argument, based on all the facts, and it is perhaps
a little humiliating to admit that the statistical evidence is deficient
because we have failed to collect it; but to do this is not only more
scientific, it is in the end more convincing, and after all there is no free
choice, because it is the only honest method, whether it be convenient or not.
Finally, it is the only way of progress, for the first step towards collecting
better evidence is to recognize the deficiencies of that which is at
hand."
More than eleven years after the initiation
of the last of these five trials, the deficiencies of their controls still
remain unrecognized. The endorsements of fluoridation by medical and dental
associations, by public health authorities, and even the recent one by the
Expert Committee on Water Fluoridation of the World Health Organization (1958),
appear to have been based mainly on the opinions of the authors and of others.
Indeed, in the report of that Committee, under the heading "Results of
fluoridation", instead of results being considered, comment was confined
to: "Reports of the results after 10 years of controlled fluoridation in
three cities". Examinations of the data obtained in these trials, which
have been published by other endorsing bodies, are also inadequate or absent.
It is an understatement to term this failure regrettable.
In 1951, Appleton stated that in any future
fluoridation trial: "The experiment should be genuine, and not one in name
only. In designing such an experiment, a careful and competent analysis of
those now in progress should first be made, in order to see how they might be
improved or extended."
In the early part of this paper some basic
experimental considerations were mentioned. In cities in which it is intended
to compare the caries attack rates of the children in a fluoridation trial, the
three main factors which should be as closely comparable as is practically
convenient are the composition of the water supply, the climate and the dental
caries attack rates. Four trials having "fluoride-free" control
cities have been considered. The composition of Newburgh's water supply is
considerably different from that of its control city. There were gross
differences between Evanston and its control city regarding the initial caries
attack rates in the younger children. In the Department of National Health and
Welfare study in Brantford, as the first examination was made over two and a
half years after the commencement of fluoridation, it cannot be known what the
pre-fluoridation rates in that city would have been, if assessed by those
examiners; thus, it cannot be determined how closely the (1945) Brantford rates
resembled those of Sarnia. In the Grand Rapids study, the fluoridation of the
water supply of Muskegon in 1951 severely limited its usefulness as the control
city.
In each trial both the test city and its
control were selected. For instance, "Oak Park graciously offered to serve
as the control community" for Evanston (Blayney and Tucker, 1948). Two
cities which had agreed to participate in the experiment, after having been
found suitable for comparison, should have been allotted at random to be test
or control. It will be recalled that in at least two of the cities selected as
test ones, Evanston and Brantford, "dental care was outstandingly
good" (United Kingdom Mission, 1953)
It has been pointed out in Part One that in
all these trials no attempt was made to devise a randomization procedure in the
clinical examinations which would have eliminated examiner bias, nor were
estimates made of examiner variability.
Two statements made by authors of these
studies may be recalled. In 1950 Hill et
al. said: "It is to be expected that the rate of caries in all teeth
varies from year to year due to chance. A significant reduction of caries
prevalence can therefore be assumed to exist only when the statistical analysis
of the data provides almost absolute certainty that the observed differences
are not due to chance." However, as was mentioned in Part One this very
important matter of random variation has been ignored in all these studies.
Blayney and Tucker (1948) stated that: "A study of this nature must have
an adequate control." It has been seen that the controls used in these
trials cannot be considered to be adequate.
It would appear that these shortcomings have
not been recognized, for those who conducted these studies, and other writers,
have expressed their satisfaction with the methods used. For instance, Ast and
Chase, the authors of the 1953 report on the Newburgh-Kingston study, referred
to "the carefully controlled studies such as the Newburgh-Kingston, Grand
Rapids-Muskegon, and the Evanston studies"; and Mather (1957) said:
"This study at Brantford was most carefully set up and has been under the
strictest control."
Approval of the methods used in these studies
was also expressed by the New Zealand Commission of Inquiry (1957), for it
considered that: "All these investigations" in Brantford, Newburgh
and Grand Rapids "were designed and executed with great
thoroughness." The Commission also said: "We have examined the
statistical evidence brought forward by the advocates of fluoridation, and the
conclusions they have drawn from that material ... We have found nothing to
invalidate the statistics or cast doubt on their reliability." It will be
realized that many of the deficiencies of these studies can be noted only when
different reports >from the same study are compared. It seems that the
Commission was handicapped in this regard, for although its "List of exhibits
produced at public hearings" mentions over 250 items, such as papers,
books, charts and letters, it includes only the final report, or the one which
was the most recently published at that time, of the numerous reports showing
the dental caries attack rates which were published in each of these studies.
It would appear that none of the earlier accounts of these trials were shown to
the Commission, nor were they mentioned in the "bibliography" of 144
references. None of the reports from the City Health Department trial in
Brantford were listed as exhibits. The paper by Brown, Kohli, Macdonald and
McLaren (1954a) which is mentioned deals only with gingival results. Although
the Commission had the assistance of legal counsel in gathering the evidence,
no mention was made of the employment of a statistician to assist its members
in evaluating the numerical data.
The Expert Committee on Water Fluoridation of
the World Health Organization (1958) also expressed its satisfaction with the
methods used in these trials. Out of the hundreds of controlled fluoridation
programmes which it stated have been set up, it mentioned only the Newburgh,
Grand Rapids and Brantford (City Health Department) studies in the sixteen
lines which allotted to the mention, one cannot say consideration, of the
results of fluoridation on dental caries prevalence. Presumably these three
trials were cited because the Committee considered that they were the most
important and reliable studies, and it said that they were "carefully
planned and controlled". As this opinion of the Committee was made in
referring to the three studies which it cited in mentioning results of
fluoridation, it is reasonable to assume, at least in this instance, that the
term "controlled" was used in its experimental sense.
If this is the case, the inaccuracy of that
statement of the Expert Committee is astonishing, for it will be recalled that,
of the three studies which the Committee quoted, the Brantford (City Health
Department) study, far from being carefully controlled, was not controlled at
all. Furthermore, the control for the Grand Rapids study was abandoned after
only six years, at the crucial stage of the trial when the first of the
permanent teeth were erupting in the children of the test city who had ingested
fluoridated water throughout their lives. Therefore the control , was abandoned
before any assessment of caries activity in those teeth could be made. In
regard to the remaining study mentioned by the Expert Committee, the Newburgh
trial, after the unexplained decreases in the DF rates for deciduous teeth,
which were shown as having occurred in Kingston, the control city, between
19456 and 1949, no further caries rates for deciduous teeth were published.
Also, the erratic changes which were made in the methods used in this trial are
not consistent with careful planning, nor is the choice as the test and control
areas of two cities with water supplies which were of considerably different
composition.
It has been acknowledged for many years that
one of the fundamental procedures in planning an experiment is the
establishment of a statistical design for the procedures before work is
commenced. The deficiencies in the basic statistical requirements of a good
experimental design are only too obvious in all these studies. Therefore, it is
surprising that the Expert Committee did not point out these deficiencies, but,
on the contrary, described the three studies which it mentioned as carefully
planned ones. The importance of these matters is emphasized by the
authoritative statement of Fisher (1951) that: "If the design of an
experiment is faulty, any method of interpretation which makes it out to be
decisive must be faulty too."
This investigation of reports of these
fluoridation trials was instituted when a preliminary examination of the
methods used revealed disturbing facts, and solely because it was felt that, as
Appleton (195 1) expressed it: "Professionals and specialists have the
duty of insisting upon a scientific demonstration of a high probability that a
proposed method will be useful and safe, before it is recommended for general
adoption. The maintenance of this attitude is of paramount importance."
The deficiencies of these trials not having
been recognized, many cities have already fluoridated their water supplies on
advice which is based largely on the results that have been considered. It is,
therefore, an important and urgent matter that a more accurate assessment of
the efficacy of this process should be obtained, but, unfortunately, it appears
that little long-term experimental evidence is available. Therefore, despite
the limitations imposed by the methods used in these studies, consideration
should be given to a careful and competent examination of the whole of the
original data obtained in them. The findings resulting from such an examination
would be of assistance in designing future fluoridation trials, and would
provide a far more adequate assessment of the results reported from these
studies than it is possible to obtain from an examination of the very limited
data that have been published.
At least until such a report is available for
examination, it would be wise to maintain an open mind in regard to the
efficacy of artificial fluoridation.
SUMMARY
1. Endorsements of the process of the
mechanical fluoridation of public water supplies rely mainly on five
experimental trials.
2. The controls used in these studies are
considered.
3. The reliability of the results reported is
affected by:
(a) odd experimental and
statistical methods;
(b) failure to consider
random variation and examiner variability, and to eliminate examiner bias;
(c) omission of relevant
data;
(d) arithmetical errors;
(e) misleading comments.
4. Controls were either doubtful or
inadequate.
5. No control was employed in one trial.
6. The published data do not justify the
statement that caries rates remained the same in control cities.
7. The sound basis on which the efficacy of a
public health measure must be assessed is not provided by these five crucial
trials.
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