ACID PRODUCTION AND TOOTH DECALCIFICATION BY ORAL BACTERIA

¹ Division of Dental Research, The University of Rochester School of Medicine and Dentistry, Rochester, New York

Cultural estimates of the numbers of acidogenic organisms in saliva from mouths with active caries, indicated that lactobacilli were a minor constituent of the oral flora.

Comparisons of the rate of acid formation by various mouth organisms showed that streptococci and actinomyces-like organisms formed acid most rapidly, and that lactobacilli and other organisms were less active in this respect. Some streptococcal strains formed acid more rapidly than others.

The addition of enamel or dentin to cultures of oral bacteria influenced differently the amounts of acid formed, apparently depending upon the pH at which the bacterial enzymes act. The streptococci fell into two groups, one forming more and the other less acid in the presence of tooth substance. The pH of cultures containing enamel or dentin never fell below pH 5, indicating that this is the critical point for tooth decalcification.

The amount of tooth tissues dissolved in cultures was directly proportional to the titratable acidity. The solubilities of various types of enamel and dentin in bacterial cultures paralleled those observed in acid solutions.