Method for Study of Saliva and Bacteria in Dental Enamel Decalcification

¹ Division of Dentistry and Oral Surgery, Henry Ford Hospital, Detroit, Michigan

A pure-culture method was devised to study effects of saliva from caries-immune and caries-susceptible human beings on bacterial decalcification of granular enamel as determined by flame spectrophotometric analysis of calcium. Rough and smooth varieties of lactobacilli, S. mitis and S. salivarius, all isolated from saliva of caries-susceptible persons, were used as test organisms.

Various aspects of the technic were explored to establish optimum conditions necessary to obtain bacterial decalcification and to detect any salivary effect on this process. The aspects of the test established were the bacterial substrate, concentration and age of the inoculum, incubation conditions, effect of initial pH, the decalcifying potential of several lactobacilli and streptococci, and the rate at which decalcification of enamel proceeded. Differences and similarities of reaction among the four classes of test organisms were recorded.

Significantly less decalcification was found to occur in the presence of immune saliva than in susceptible saliva. Certain conditions were shown to enhance this observed difference between the two types of saliva. The test satisfactorily demonstrated the close correlation between titratable acidity and calcium solution from enamel, as well as the critical pH (pH 5) required for significant enamel decalcification.