Salivary pH-rise activities in caries-free and caries-active naval recruits

Kleinberg (1967) (Archs oral Biol. 12, 1457-1473) has observed that the incubation of a salivary sediment/supernatant mixture with a low concentration of glucose produces a pH drop followed by a pH rise. As this pH-rise effect could elevate oral pH in vivo, the degree of such activity could be directly related to caries resistance. The pH-rise of paraffin-stimulated whole saliva samples from 54 caries-free and 54 caries-active male naval recruits was compared in two assays. The first, conducted with sediment/supernatant/2.8 mM glucose mixtures, showed no significant differences for mean pH versus time profiles for 26 caries-free and 26 caries-active subjects. Concomitant assays, in which 3.33 mM arginine and water replaced the supernatants in the assay mixtures, showed slightly higher mean pH/time profiles, with higher minima for the caries-free subjects. These profile differences were statistically significant for the arginine-containing mixtures, a result attributed to different microbial distributions for the caries-free and caries-active sediments. The second assays were conducted on saliva supernatants from 28 caries-free and 28 caries-active subjects, employing a strain of Lactobacillus casei in place of salivary sediment in the assay system. No statistically significant differences were evident between the mean pH/time profiles for the two groups of subjects, although a significant positive correlation was observed between pH minimum and bicarbonate content of the samples. Thus no relationship of salivary pH-rise activity and caries experience were found.