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.

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Abstract--InMarch 1953 water-fluoridation was started in Tiel, the Netherlands. From the caries numbers of three age classes the differences in caries inhibition for the various teeth and for the various tooth surfaces are shown after 54 years of fluoridation.The free smooth surfaces (buccal and labial) show an important caries reduction even if fluoridation started some years after the eruption of the tooth. If waterfluoridation is started 2 or 3 years before eruption the differences are hardly any greater.Some proximal surfaces show a reasonable caries reduction if water-fluoridation is started shortly after eruption. The degree of protection seems partly determined by the accessibility of the surface for fluoride ions and the condition in the interproximal space. A pre-eruptive period with fluoridated drinking-water increases the effect substantially.For the occlusal surface, only an insignificant effect was found if fluoridation was started after eruption. If fluoridation is started 2-3 years before eruption the caries inhibition was still about 50 per cent smaller than for the proximal surfaces. Only in those premolars and second molars which at the start of fluoridation were in an early stage of development, a larger caries inhibition for the occlusal surface was found.The caries inhibition in the various surfaces seems to be correlated with the degree in which fluorine ions can be built in or absorbed by the enamel of these surfaces.