“…It has been suggested that such lesions can adapt to become areas of increased resistance to further car ious attacks [Koulourides et al, 1980], Le sions in contacting approximal surfaces should be capable of exactly the same be haviour under the right conditions. Lon gitudinal radiographic studies have re vealed that caries progression is normally a slow process, but that groups with access to fluoride supplements exhibited even slower progression [Pitts, 1983a], This ef fect and the increased number of 'rever sals' seen in fluoride groups may be due to an increase in the rate of remineralization [Goaz et al, 1963]. Leijon [1969] has de scribed an appearance similar to the ra diopaque islet seen in figure IB but in his case it was seen only on a microradio graph of an extracted molar, all clinical radiographs of which were scored sound.…”