COMPARATIVE MICROFLORA OF DEVELOPING DENTAL PLAQUES IN CARIES-IMMUNE AND SUSCEPTIBLE INDIVIDUALS

¹ Dental Research Laboratory and Department of Bacteriology, The Ohio State University, Columbus, Ohio

1. A method is described for dispersing dentobacterial plaque material in liquid media by means of ultrasonic agitation. The technic is simple and rapid, and gives reproducible results.

2. Comparative examination of several types of bacteria in dispersed plaque material from caries-immune and susceptible human beings showed the most striking difference to be in the low occurrence of lactobacilli in immune subjects with low salivary lactobacillus counts. The typical immune individuals have few or no lactobacilli in saliva or plaques. Plaques from those few immune subjects with high salivary lactobacillus counts resembled plaques from susceptibles.

3. Comparison of developing plaques in caries-immune and susceptible groups showed differences in rate of increase of several types of organisms, including lactobacilli. The data indicate that in immune persons with low or negative salivary lactobacillus counts, the mechanisms responsible for this condition may also affect organisms in dental plaques.