Marshall L. Snyder

A Simple Colorimetric Method for the Estimation of Relative Numbers of Lactobacilli in the Saliva

This paper includes the results of an attempt to develop a simple colorimetric method for the estimation of the relative numbers of lactobacilli in the saliva as a supplementary procedure for the quantitative techniques (1, 2) used in the study of dental caries. The test was based on the assumption that since caries activity is closely correlated with the numerical rise and fall of lactobacilli in the saliva, it should be possible to demonstrate a corresponding increase and decrease in the amount of acid produced in a selective carbohydrate medium inoculated with definite amounts of saliva. Thus, significant color changes in selected time intervals could be interpreted roughly in terms of lactobacilli per c.c. of saliva as established by an adequate number of control plate counts. The present data embodies a large series of tests on specimens of saliva sent to the School of Dentistry of the University of Michigan for estimation of numbers of lactobacilli.

Acid Production of Oral Bacteria Associated with Dental Caries

A controversy still exists over the organism or organismns of the oral flora responsible for the acid that must be produced to decalcify the enamel and dentin in carious lesions. One group (1-6) holds that a single species or type (L. acidophilus) which not only can produce but also maintain an acid environment sufficient for in vivo decalcification (pH 5.0) is primarily responsible. Others (7-11) feel that the action is essentially non-specific and depends on the acidogenic powers of any one or combination of bacteria. Hence, it was thought of interest to report some simple experiments dealing with the aciduric and acidogenic properties of strains of oral lactobacilli, yeasts, streptococci, and staphylococci, which are the organisms most commonly associated with dental caries.