A prevalence study simply counts noses, or in this case spots on teeth. Such an accounting alone does not say much of anything regarding the alleged safety of water fluoridation. Any claims made as a result of such a study are arbitrary. Prevalence data are not neutral but require an interpreter. Indeed, effects at a cellular level cannot be accounted for in these studies. So the assumption is made that since we do not see any problem (e.g. no dead bodies) then there must not be any problem. But the underlying assumptions are arbitrary. Change the assumptions and the interpretation of the prevalence data will be very different indeed.
Büchel K, Gerwig P, Weber C, Minnig P, Wiehl P, Schild S, Meyer J. Prevalence of enamel fluorosis in 12-year-olds in two Swiss cantons. Schweiz Monatsschr Zahnmed. 2011;121(7-8):647-56. [Article in English, German]
The neighbouring cantons Basel-Stadt and Basel-Landschaft had introduced different fluoridation schemes for caries prevention: Basel-Stadt provided drinking water fluoridated at 0.8-1 ppm F since 1962, while Basel-Landschaft introduced fluoridated domestic salt (250 ppm F since 1983). Representative samples of 12-year-old schoolchildren (6th-graders) were studied to evaluate the prevalence of (I) dental fluorosis (FOP) using the Thylstrup-Fejerskov (TF) index, (II) non fluoride-associated enamel opacities (non-FOP), and (III) hypoplasia of the incisors. Standardised frontal colour photographs were taken and assessed by four examiners after projection. Of 373 schoolchildren studied in 1999 in Basel-Stadt 119 (31.9%) showed fluoride-associated enamel opacities, i. e. 66 (17.7%) a very mild form (TF score 1), 47 (12.6%) a mild form (TF score 2), five scored TF3 and one TF5. In addition, non-FOP were diagnosed in 115 (30.8%) and hypoplasia in 47 (12.6%) children. Among the 448 children evaluated in 2001 in Basel-Landschaft 143 (31.9%) showed FOP, namely 74 (16.5%) scored TF1, 54 (12.2%) scored TF2, 12 (2.7%) scored TF3, and three (0.7%) scored TF5. Non-FOP were found among 93 (20.8%) and hypoplasia among 56 (12.5%) children. Thus, in spite of different fluoridation schemes in the two cantons, the prevalences of FOP were identical. Most fluoride-associated enamel opacities were mild or very mild. They did not represent an aesthetic problem and certainly not a public health concern.
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