Rates of formation in vitro of dental caries-like enamel lesions in man and some non-human primates

Abstract

The relative susceptibilities of the enamel of man and of 4 non-human primates, all with similar enamel structure, to a standard acid challenge were assessed by measuring the rates of progression of subsurface, caries-like lesions induced in vitro by exposure to acidified gels. The histology of all the artificial lesions was similar to that of natural carious lesions in man. In the experimental lesions, the depth of penetration was directly proportional to the square root of the time of exposure to the acid gel. At pH 4.5, the rate of lesion formation was greater in enamel of the non-human primates than in that of man and for rhesus macaque enamel the difference was significant at the 1 per cent level. The difference in lesion penetration combined with the relative thickness of the enamel means that, in macaque teeth, lesions would reach the enamel-dentine junction approximately 5 times as fast as in human teeth. A small, measured difference in fluoride concentration between these two species is unlikely to account for the difference in susceptibility; more likely it is due to the lower porosity of human enamel. At pH 5.0, lesion penetration seemed to be the same in macaque and human enamel, and at pH 5.5 penetration seemed to be faster in human enamel.