Geochemical provinces and the incidence of dental diseases in Sri Lanka.

A survey carried out on the incidence of dental diseases and the distribution of fluoride in drinking water wells in Sri Lanka shows that 3 areas in particular had abundant fluoride (greater than 2ppm). Dental fluorosis was common in areas with high fluoride content while those areas with very little or no fluoride, such as the central region of Sri Lanka, had a high incidence of dental caries. The intensity of rain fall played a major role in the leaching of fluoride ions from soils and it is perhaps this factor which is responsible for the occurrence of a low fluoride zone in the central part of Sri Lanka. The presence of areas containing high fluoride and hence dental fluorosis coincided with geochemical provinces. In these areas, mineral deposits such as apatite and serpentine and also hot spring regions with exhalations of fluorine are found.