STUDIES OF THE RESPIRATION OF THE MICROBIAL FLORA OF HUMAN SALIVA

¹ Department of Dental Research, Army Medical Service Graduate School, Walter Reed Army Medical Center, Washington, D. C.

The viable microbial flora is principally responsible for the respiration rate of whole, stimulated saliva. The respiration rate of the microbial flora of whole saliva is depressed by the partial removal of its microbial flora or is inhibited by substances which render the bacteria nonviable. The oxygen consumption of the microbial flora of whole, stimulated saliva is not correlated with susceptibility or immunity to dental caries. In a majority of cases, the rate of oxygen consumption of the microbial flora of saliva does differ significantly from one individual to another. The addition of mono- and polysaccharides to stimulated saliva in vitro causes an increase in the respiration rate of the microbial flora. The addition of glucose to saliva causes an apparent increase in respiration over the addition of starch, but a statistical evaluation of the percentage increase in respiration caused by the two carbohydrates shows no significant difference in their effect on this rate.

Concentrations of fluorides up to 200 p.p.m. have little effect on the rate of oxygen consumption of the microbial flora of saliva to which no carbohydrates have been added. Fluoride in concentration of 200 p.p.m. did have a moderately depressing effect on the oxygen consumption of the microbial flora of saliva to which carbohydrate in a final concentration of 2 per cent had been added. With the exception of calcium fluoride, all fluorides studied, when added to stimulated saliva in final concentration of 1.6 per cent, depressed oxygen consumption by amounts ranging from 44 per cent to 78 per cent. Calcium fluoride, in a concentration of 1.6 per cent, caused a decrease in oxygen consumption of less than 10 per cent.