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In 1973 the fluoridation of drinking water in the Dutch town of Tiel was discontinued. In order to monitor the effect of this measure, the caries experience in 15-year-old children was investigated annually from 1979 to 1988, both in Tiel and in Culemborg. In the latter town the drinking water had never been fluoridated. The caries data of 15-year-old children examined between 1968 and 1969 in Tiel (children having used fluoridated water from birth) and Culemborg were used as historical controls. In Tiel the mean number of DMFS increased between 1968/69 and 1979/80 from 10.8 to 12.7 (+18%) and decreased to 9.6 (-26%) in the following years; in 1987/88 the mean DMFS was 11% lower than in 1968/69. In Culemborg the mean DMFS score decreased between 1968/69 and 1987/88 from 27.7 to 7.7 (-72%). In 1968/69 the mean DMFS score in Tiel was 61% lower and in 1987/88 17% higher than in Culemborg. The question as to whether water fluoridation would have had an additional effect if it had been continued (presuming the application of existing preventive measures) cannot be answered, as there are no remaining communities with fluoridated water in The Netherlands.

A study was executed to investigate the relation between the use of fluoride tablets by children in the age period 1.5-6 yr on the one hand and the caries experience at the age of 6 and 15 yr and the prevalence of fluorosis at the age of 15 yr on the other hand. The year of birth of the child, the motivation of the mother to engage in preventive dental behavior, the level of her school education and her place of birth were taken into account as possible confounding factors. A significant relation was found between the use of fluoride tablets and the prevalence of fluorosis. The most important predicting factor for the caries experience of the child was the mother's motivation to engage in preventive dental behavior. An effect of fluoride tablets on the caries experience could not be demonstrated.

At the end of 1989 the organisation for dental health education in The Netherlands 'Ivoren Kruis' presented new recommendations about the use of fluorides. The advice was based on a report of an expert committee and was put in a definite form in consultation with representatives of a number of dental and medical professional organisations. For children below the age of five a toothpaste with 250 ppm F- is recommended. Fluoride tablets (with 0.25 mg F-) are recommended for children below the age of 12. The advised number of fluoride tablets is reduced compared with the former recommendations.

Dental caries induced by infection with Strep. mutans C67-1 (serotype c) or Strep. mutans 50B4 (serotype d/g) and feeding a 30 per cent sucrose-containing diet was found mainly in fissures; smooth surface caries was not detected. A decrease in the mean caries score was observed with time, coinciding with lower recoveries of Strep. mutans at the end of the experimental period. The decrease in caries formation may be attributed to changes in some of the cariogenic properties of the individual Strep. mutans strains during maintenance in the laboratory, as re-isolation of the strains from caries-active mice yielded similar and reproducible caries scores to those in early experiments. Hence Balb/c mice can be used as an experimental model in caries research, provided that great care is taken in selecting and storing the bacteria.

Plaque samples from caries-active subjects showed a higher incidence of S. mutans than plaque samples from caries-free subjects. This was especially evident in approximal incisor plaque. S. mutans serotype d was almost exclusively present in approximal plaque obtained from caries-active subjects. Tooth surfaces infected with S. mutans still harbored this micro-organism 10 months later, while uninfected tooth surfaces remained free of S. mutans. Caries development predominantly occurs on those tooth surfaces which harbor relatively high percentages of S. mutans (> 5%). It is unlikely that serum or saliva antibodies against S. mutans play a major role in the protection against dental caries in these caries-free subjects since subjects with the greatest number of decayed surfaces showed the highest antibody titre as measured by haemagglutination or by the enzyme-linked immuno sorbent assay (ELISA).

A survey was done of the prevalence of dental fluorosis among children aged 7-16 years and the occurrence of skeletal fluorosis among adults aged 40-60 years living in regions in Senegal where fluoride concentrations in the drinking water ranged from less than 0.1 to 7.4 mg/l. In the area where the fluoride concentration in the drinking water was 1.1 mg/l milder forms of dental fluorosis were found, the prevalence being 68.5%. In areas where fluoride concentrations exceeded 4 mg/l the prevalence of dental fluorosis reached 100%. Kyphosis was very prevalent among a community whose drinking water contained 7.4 mg/l fluoride. Radiographs of the vertebral column, hand, and wrist of 3 adults with kyphosis confirmed the diagnosis of skeletal fluorosis. High sweat loss and a high intake of water because of the hot weather may account for the finding. The present World Health Organisation guideline for the upper limit of fluoride concentration in drinking water may be unsuitable for countries with a hot, dry climate.