The results of 6 1/2 years of artificial fluoridation of drinking water in The Netherlands : The tiel—Culemborg experiment

In order to assess the effect of water fluoridation on dental caries under Dutch living conditions (food, water consumption, etc.) the drinking water of Tiel was fluoridated since 1953 at 1·1 mg/l. The nearby city of Culemborg served as control (±0·1 mg natural fluoride per litre of water). The principal study groups contained each second year the 11–15 year old children from both cities. Approximal caries was estimated from radiographs only, caries of occlusal and free smooth surfaces in a clinical examination. Both methods were standardized as far as possible. The results after 6 1/2 years of water fluoridation show an important caries inhibiting effect on caries of approximal and free smooth surfaces. The inhibition of occlusal cavities is (at the present time) far less marked. The favourable effect of this water fluoridation is in many respects similar to the results of American studies after the same interval

Some special features of the caries preventive effect of water-fluoridation

In March 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 5 1/2 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 water-fluoridation 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. The degree of caries inhibition found will partly depend upon the methods used for the caries examination. In general, percentages of caries reduction tend to be higher if caries is diagnosed in a more advanced stage