Changes in caries prevalence in Japan.

In Japan, the mean DMFT at 12 years of age increased from 2.8 in 1957 to 5.9 in 1975. From the 1981 survey (DMFT = 5.43), conversely, the mean DMFT decreased and reached 3.64 in 1993. The increase in caries prevalence can, without doubt, be explained by an increment of sugar consumption, since the intake of sugar increased after World War II and exceeded 18.25 kg/year (50 g/day) in 1965 and reached a maximum value (29.3 kg/year) in 1973 in Japan. On the other hand, the reason why the DMFT has decreased since 1981 is not clear. In many industrialized countries, a caries reduction has been achieved with acceptable fluoride exposure, although sugar consumption was still at a high level. However, fluoride usage was still limited during the last 2 decades in Japan. There is no community where fluoridated drinking water has been supplied since 1972. Fluoride tablet use was also discontinued for children in the 1970s. Fluoride mouthrinsing programs were available for only 1% of school children in 1992. Moreover, the market share of fluoridated dentifrices stayed at 10% until 1986 and became 30% only in 1988. An excellent correlation (r = 0.91; P < 0.01) is observed between the DMFT in 12-year-olds and per capita sugar consumption per year between 1957 and 1987 in Japan.