The effect of fluoridation on the occurrence of hidden caries in clinically sound occlusal surfaces.

It has been suggested that the diagnosis of occlusal dentine carious lesions has become more difficult due to the influence of fluoride on the character of pit and fissure surfaces. The issue pertains to the occurrence of hidden caries exemplified by occlusal surfaces judged as clinically sound but showing a radiolucency on the bite-wing radiograph. The aim of this study was to investigate the influence of water fluoridation on the occurrence of hidden caries in clinically sound occlusal surfaces in young people. The data of 515 persons (15 years of age) collected in 1968/1969 as part of the Dutch longitudinal epidemiological Tiel/Culemborg study were used. The participants in Tiel (F) were exposed to artificially fluoridated drinking water (F-concentration 1.1 ppm F) from birth until the end of the data collection. The participants in Culemborg (NF) were not exposed to extra fluoride (F-concentration 0.1 ppm F). In 1994 the status of occlusal surfaces of the first and second molars, as read from bite-wings made in 1968/1969, were judged by 2 investigators. (Cohen's Kappa intra- and inter-examiner agreement 0.90, 0.83 and 0.85, respectively). The original clinical data of 270 inhabitants of Tiel (F) and 245 of Culemborg (NF) were compared with the radiographic judgements. The children examined in Tiel (F) had a mean of 2.54 clinically sound occlusal surfaces in first and second molars (including surfaces with an enamel demineralization only) of which bite-wing radiographs detected 0.43 surfaces (16.9%) with a radiolucency into dentine. In Culemborg (NF) the children had a mean 0.65 clinically sound judged surfaces of which 0.16 (24.6%) showed a radiolucency on the bite-wing films. The results of the investigation show a proportional reduction of surfaces with hidden caries among clinically sound surfaces in the fluoridated area compared to the control.