FIGURE 8-1 Relationships among caries experience (solid line), dental fluorosis index (dashed line), and the fluoride concentration of drinking water. A fluorosis index value of 0.6 was judged to represent the threshold for a problem of public health significance. The data are based on the examination of 7,257 12- to 14-yearold children (Dean, 1942).

lier children are exposed to fluoridated water or dietary fluoride supplements, the greater the reduction in dental caries in both the primary and permanent teeth (Hargreaves et al., 1988; Lewis, 1976; Stephen et al., 1987).

A large number of studies have shown that fluoridated drinking water increases resistance to dental caries at all ages. For example, Jackson et al. (1973) recorded caries experience among 3,902 residents of York and Hartlepool, England. The water fluoride concentrations in these cities were 0.2 mg/liter and 1.5 to 2.0 mg/liter, respectively. Caries experience in people in five different age groups (ranging from 15 to 19 to > 44 years) was significantly lower in Hartlepool (44 percent lower in the > 44-year-old group). In a study of Swedish subjects aged 30 to 40 years (n = 496), who were life-long residents of Uppsala (1.0 mg/liter fluoride in water) or Enköping (0.3 mg/liter fluoride in water), Wiktorsson et al. (1992) found that