Saarbruecken, November 21, 1999

Dear Panel members,

Looking over the list of studies to be included in a review that "should be looking at the size and distribution of the positive and negative effects of water fluoridation, and assessing the impact of potential effect modifiers such as the type of fluoride, dose, other sources of fluoride, socio-economic and behavioural factors etc", your reference No. 118 immediately caught my eye. You give this reference as:

  • Klein H.: "Dental caries (DMF) experience in relocated children exposed to water containing fluorine". J. Am. Dent. Assoc. 1946, 33: p. 1136-1141

   However, this is part II of a series of two articles by Dr. Henry Klein, Division of Public Health Methods, U.S.P.H.S., on the subject. The actual title is:

  • "Dental caries (DMF) experience in relocated children exposed to water containing fluorine. II"

   After looking at your list of references, what is (or was) anticipated by many people to become a fair and objective review of the matter appears to me just as another preconceived study aimed to prove the safety and efficacy of fluoridation. One more indication may be your omission of the "II". Was this done, perhaps, lest some people might ask you about part I, which was published in Public Health Reports in 1945?

  • Klein H.: "Dental caries experience in relocated children exposed to water containing fluorine. I. Incidence of new caries after 2 years of exposure among previously caries-free permanent teeth."; Public Health Reports 60 (Dec. 7, 1945) pp. 1462-1467

   The Klein study you cite is often used to back claims that fluoride is effective even if applied after eruption of the permanent teeth. How did he prove this?

   He reports on dental examination of persons of Japanese ancestry residing in so-called "war relocation authority centers" (i.e. concentration camps). Early in 1942 the children, because of their Japanese ancestry, had been transferred with their parents from homes in Los Angeles and environs to an assembly center near Los Angeles. Part I says: In the autumn of 1942 they were again transferred, 120 to a center in California and 196 to Arizona. While the children relocated to the California center consumed water with about 0.1 ppm fluoride, those in the Arizona center consumed water with about 3 ppm fluoride. Klein's dental examinations were done in 1943 and again in 1945. "During the 2-year interval, the children were restricted to their respective centers, since movement in and out was controlled by military authority. Their diets were quite similar and adequate."

(Let's put aside the -unanswered- question how he assured himself that the diets were "quite similar" and adequate)

   By this time, the U.S.P.H.S. Drinking Water Standards state under section 4.21.: "The presence of ... fluoride in excess of 1.0 p.p.m. ... shall constitute ground for rejection of the supply." [Public Health Reports 58 (Jan. 15, 1943) pp. 69-111). Accordingly, part I mentions a defluoridation attempt: "Because of the relatively high fluorine content of the water in the Arizona center, an attempt was made by the Relocation authority to remove the fluorides. Bone-meal filters were installed only at selected water outlets to which the population had to travel to obtain fluoride-free drinking water. After a trial of several months, treatment of the water in this manner was discontinued. Bottled fluorine-free waters were shipped into the center and sold to residents who reserved such water chiefly for the preparation of dietary formulae for infants. The children of school age obtained their drinking water from the nearest tap, which provided water containing fluorine (except during the 3-month period mentioned above, when fluorine-free water could be obtained, if so desired, at several selected outlets)."

   If we put aside the ethical aspects of this affair and the Klein study, there are other aspects which the Committee shouldn’t overlook. For in part II we read: "The 196 boys and girls residing at the California center from 1943 to 1945 consumed water containing only 0.1 part per million of fluorine (a value within the error of determination). In contrast, the 120 children residing at the Arizona center over the same time interval consumed water containing fluorine to the extent of 3 parts per million".


Part I.: 196 girls and boys relocated to Arizona, 120 to California. Part II: 120 girls and boys relocated to Arizona, 196 to California

[Ed: Numbers reversed!]

So, please tell me which of those is the group designated as the "Fluoride" group? Do you identify them in Klein's tables with the aid of their caries experience (which, of course, was to be examined)?

Just looking at his tables calls to mind another effect he himself once had described and which was confirmed by many dental researchers and even acknowledged by the American Dental Association:

  • "News editors _are_ interested in dentistry whenever dentistry is news. Witness the stories entitled ... "girls teeth are more susceptible to cavities and other dental disorders than those of boys" which have been carried recently by the leading news services"   ("Dentistry and the magazine editor", J. Am. Dent. Assoc. 28 (1941) 991)


  • "Many investigators have noted that the incidence of caries is significantly higher in girls than in boys. Palmer and Klein have suggested that this difference can be attributed to the earlier eruption of the teeth of girls. Sloman did not agree with this view. ... Adjusting the ages of boys to compensate for the earlier eruption of teeth in girls does not nearly account for the higher susceptibilty of girls to caries. Sloman reasoned that if a longer period of exposure were the only factor there would have to be a difference of more than two years in the average age at which the individual teeth erupt in the two sexes. Actually, the difference is only four-tenths of a year." [Gruebbel A.: "Caries Control: Public Health Aspects"; J. Am. Dent. Assoc. 37 (Oct. 1948) 426].

 Sloman argued that,

  • "From data previously published, it is evident that girls, at least for the age groups under consideration (12 to 18 years of age), endeavor to, and actually do, take better care of their teeth than do boys of the same age levels. Boys, although they have a greater number of untreated carious teeth present at each of the age levels under consideration, have a smaller number of filled teeth, a smaller number of teeth lost through caries, and a smaller number of teeth attacked by caries. These facts indicate that oral hygiene habits, including dental care, are much more satisfactory in girls than in boys of these age levels and are not demonstrable factors in reducing the frequency of attacks by caries. The value of such habits, however, cannot be overestimated in the reduction of the prevalence and in the control of this disease." [Sloman E.:" Sex and age factors in the incidence of dental caries"; J. Am . Dent. Assoc. 28 (March 1941) pp. 441-444].

Suffice it to add here that Dr. Sloman's view is also reflected in the data of the 1933-1934 dental caries survey (Public Health Bulletin 226 (1936), of which H. T. Dean was a co-editor) and that probably the "past treatment" part of the DMF (i.e. the missing and filled teeth) has also to do with the dentist - population ratio which differs widely from region to region.

   Back to Klein's tables. Somebody interested in his data could not overlook (table 1 of part II) that his so-called "Control Group" (of which we do not know for certain whether or not it is the control) has a much higher girls to boys ratio than his so-called "Fluoride group". This imbalance must certainly lead to a higher DMF-Index in the control (decayed, missing or filled teeth per 100 _CHILDREN_ ). Please note that this is not the first and not the only time that the composition of samples (groups of children) has been misused to construct a caries-protective effect of fluoride!

   Please also note that this pertains to one of the important questions asked by the PFPC in Canada in their Open Letter #3, which has been posted at


Well, I do not want to teach the York Committee how to do its job. But I for one would start with a review of the advantages and disadvantages of the DMF-index as invented by Klein and (mis)used in the dental literature.

Yours sincerely,

Peter Meiers