(Published by Health Canada, Health Protection Branch, July 2, 1994)
Reviewed by: Richard G Foulkes BA MD
Two conditions were imposed. They were to use: total fluoride intake (air, food, water) provided to them by Health Canada, but to refrain from publishing these data or otherwise making them public; and, relevant Canadian studies as much as possible. Intakes were to be reported as micrograms fluoride per kilogram body weight per day (ugm fluoride/kg bw/day).
The author responsible for the assessment of the effectiveness of the various methods of delivery of fluoride, presents a "review of reviews". He points out that many of the studies are contradictory and produce variable results. Nevertheless, with little evidence to support his conclusions except for "opinion" handed down from one historical review to another, he reports that the effectiveness of water fluoridation has "decreased" to 30% and rates the topical delivery methods as: operator applied liquids or gels (12,000 ppm), 30%; fluoride dentifrices (1000 ppm), 25%; fluoride mouth rinses, 28%. This author suggests lozenges as a safer supplement alternative to tablets and credits both as being 20%-30% effective.
Dose response in prevention of caries and dental fluorosis A finding that is well supported by contemporary North American studies is the increased prevalence of dental fluorosis. This report, on the basis of a review, shows a mean score of 40.5% for fluoridated and 20.4% for non-fluoridated North American communities and points to the underestimation by the US Public Health Service. The authors appear united in the view that dental fluorosis is cosmetic. One of them is convinced that there is no social concern regarding dental fluorosis and that the increase is of only "scientific interest".
The studies of the efficacy of fluoride in the reduction of dental caries are selected. Large population studies showing negative relationships are omitted. In spite of this advantage, the authors could not find significant studies in either the US or Canada to support their belief in "benefit'. The most acceptable study, in their view, is the 1986-1987 dental survey of US schoolchildren carried out by the US National Institute of Dental Research. However, this study showed a comparable decline in caries in both fluoridated and non-fluoridated populations, and the differences were not significant.
As a result of the lack of contemporary supportive data, the authors base all of their major responses on the 1940s data of Trendley Dean's study of 21 cities as modified by Eklund's and Striffler's study (1980) that added further 1940s data from an additional 20 cities. From the curve derived from these data, the authors establish the "optimal intake" (ie, the concentration, in water, to give maximum benefit with minimal dental fluorosis) as a range of 0.8-1.2 ppm. The authors reason that because of the small amount of fluoride present in food at the time of Dean's study, this same range can be accepted to represent the optimal in terms of total fluoride intake in milligrams per day in the age group (12-14 years) studied by Dean. In brief, this report argues that Dean's original curve, modified slightly by Eklund and Striffler, is valid today provided that the abscissa is changed from ppm fluoride in water to milligrams of fluoride ingested from all sources.
The recommended total intakes in ugm fluoride/kg bw/day, as requested by Health Canada are calculated from the 1940s data. For the age group 7 months - 4 years of age, they recommend 56-81 ugm fluoride/kg bw/day. This exceeds, at the upper end, the "generally applied standard" of 70 ugm/kg/day (NRC 1993). At this range, the authors are satisfied with a prevalence "very mild" and "mild" dental fluorosis of 16-26%.
Estimates prepared by the Canadian Environmental Health Directorate in 1992 of fluoride ingestion for various routes of exposure may have been the data presented to the authors. These show that total fluoride ingested from ambient air, food, soil, and drinking water by the 7 month-4 year age group (average weight 13 kg) in ugm fluoride/kg bw/day is 67.25-100.42 in "fluoridated" areas and 25.41-36.42 in "non-fluoridated" areas. Estimates of the fluoride ingestion from twice daily use of fluoride dentifrice presented in the Environmental Health study is, for the same age group, 20-60 ugm/kg/day This compares to 18.5-43.1 ugm fluoride/kg bw/day m the report under review. Using the upper range (43.1) for this age group, total fluoride ingestion, including dentifrice, in ugm/kg bw/day is 143.52 in "fluoridated" and 79.52 in "non-fluoridated" groups. Use of fluoride supplements (1993 recommendation) by the latter would increase the fluoride intake by a further 15.8 ugm/kg bw/day for a possible total of 95.31 ugm/kg bw/day. If these calculations are correct, total fluoride intake for this important age group exceeds the recommended standard of 81 ugm/kg bw/day in both "fluoridated" and ''non-fluoridated" groups.
Health Canada may have been motivated by concern about the obvious increase in fluoride ingestion in both "fluoridated" and "non-fluoridated" communities created by the addition of fluoride to drinking water and the importation of foods and beverages prepared in "fluoridated" areas. It may also have been motivated by concern over additional fluoride from dental products and the rising rate of dental fluorosis, which they term "an adverse dental health effect".
The authors of the report express concern that water fluoridation may be threatened. By virtually ignoring the increase of fluoride in food and beverages associated with water fluoridation, they concentrate on "discretionary sources" in their recommendations in addition to suggesting that fluoridation levels be decided by regional officials on the basis of caries prevalence, a vague procedure at best.
The most prominent feature of this report is the admission of the authors that they could find no contemporary data to support the fluoride-caries hypothesis so that they were forced to base their responses on 1940s data that are more mythical than factual. Examination of the pivotal figures for a recommended range of total intake (all sources), the optimal level for fluoridation and their acceptance of a 16-26% prevalence of "very: mild" to "mild" dental fluorosis leads to a serious conclusion: the authors began the report with a determination to recommend maintenance of the status quo and selected their data accordingly. This report appears to qualify as an example of the "tainted truth.
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