Development of rampant dental caries, and composition of plaque fluid and saliva in irradiated primates.

Co-60 gamma irradiation of the salivary glands of Macaca mulata monkeys fed a cariogenic diet led to the rapid onset of dental caries resembling that in irradiated human patients. Plaque fluid and saliva were sampled from irradiated monkeys, nonirradiated controls and a group of animals fed a noncariogenic diet in order to look for changes which might occur in inorganic composition related to the caries development and to dietary differences. Salivary calcium and phosphate levels were not markedly changed after irradiation: iodide levels were raised, while thiocyanate levels fell. In plaque fluid, calcium concentrations were not affected by irradiation, but were higher in animals fed a noncariogenic diet. Phosphate levels were higher with a cariogenic diet and further increased in irradiated animals. Magnesium levels were occasionally higher than those of calcium. Other differences in plaque fluid composition may be related to secondary effects of the concomitant gingival disease. The results do not point clearly at a specific change in the quality of the saliva produced by the residual gland tissue after irradiation which precipitates the rampant caries. It is more likely that the great reduction in the quantity of saliva with its protective constituents is responsible.