search, indicate that water fluoridation continues to be of major importance in the control of dental caries.

ESTIMATING REQUIREMENTS FOR FLUORIDE

Selection of Indicators for Estimating the Fluoride Requirement
Dental Caries

The cariostatic effect of fluoride is a strong indicator for an Adequate Intake (AI) of the ion. Figure 8-1 summarizes the results of the pioneering epidemiological studies of the relationships between the concentration of fluoride in drinking water and dental caries and enamel fluorosis (mottling) (Dean, 1942). Enamel fluorosis is caused by excessive fluoride intake but only during the preeruptive development of the teeth. A fluorosis index value of 0.6 in a community was judged to represent the threshold for a problem of public health significance. As can be seen in Figure 8-1, this value occurred in communities having water fluoride concentrations in the 1.6 to 1.8 mg/liter range. The figure also shows that reduction in the average number of dental caries per child was nearly maximal in communities having water fluoride concentrations close to 1.0 mg/liter. This is how 1.0 mg/liter became the “optimal” concentration. That is, it was associated with a high degree of protection against caries and a low prevalence of the milder forms of enamel fluorosis. The average dietary fluoride intake by children living in optimally fluoridated communities was (and remains) close to 0.05 mg/kg/day (range 0.02 to 0.10 mg/kg/day; Table 8-1).

Both pre- and posteruptive exposures to fluoride have cariostatic effects (Dawes, 1989; Hargreaves, 1992; Horowitz, 1990). Based on data from their long-term study of the cariostatic effects of fluoridated water in the Netherlands, Groeneveld et al. (1990) concluded that: (1) the best effect on dental caries in the permanent teeth was achieved when fluoride was consumed from birth, (2) about 85 percent of the greatest reduction in caries was obtained when fluoride consumption started between ages 3 and 4, (3) about 66 percent of the protective effect for surfaces with high caries susceptibility (pits and fissures) derived from preeruptive fluoride exposure, and (4) about 25 percent of the protective effect for the lower risk, smooth surfaces was attributable to preeruptive fluoride exposure. Several other retrospective clinical studies have shown that the ear-



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