THE pH LEVELS ATTAINED BY COMPACT LAYERS OF ORAL MICROORGANISMS IN CONTACT WITH GLUCOSE SOLUTIONS

¹ Tufts College Dental School, Boston, Mass.

The pH differential produced by samples of dental plaques and by synthetic plaques prepared from pure strains of oral microorganisms have been determined under controlled conditions of thickness, buffer capacity, sugar concentration, temperature, and pH of surrounding solution. Natural dental plaque material has been found capable of producing pH differentials of approximately two units. Larger differentials can be attained by some oral lactobacilli and streptococci. Equivalent differentials were attained by 5 other isolates. The specific acid production rate of plaques obtained from upper and lower teeth was found to be the same in contrast with the in vivo findings of other investigators. The results suggest that streptococci play a predominant role in acid formation rate and that lactobacilli have a minor part because of their less frequent occurrence and lower numbers.