FURTHER STUDIES OF A DIFFERENTIAL CULTURE TECHNIQUE FOR ESTIMATIONS OF ACIDOGENIC BACTERIA IN SALIVA

I. COMPARISON WITH CONVENTIONAL TECHNIQUES AND CONCURRENT CLINICAL EXAMINATIONS

¹ Northwestern University Dental School, Departments of Bacteriology and Pedodontia, Chicago, Ill.

A group of orphanage children, the majority 3 to 11 years old, were followed by annual clinical and bacteriologic examinations; 87 children for one year and 53 for two years. The figures for the standard tomato agar count, the Snyder test, and the acidogenic count introduced by Davies, Slack, and Tilden (DST medium) were compared statistically with the progress of caries, as indicated by the number of new carious lesions revealed by clinical and radiographic examination. The findings corroborated once more the striking association of carious conditions with the presence of large numbers of lactobacilli in the saliva. A similar striking parallelism was observed in a one year study of a group of 25 teen-age girls.

Streptococcus counts on DST medium were very high in all the children studied, irrespective of clinical conditions; there was no indication in these experiments that the streptococci are significant in relation to dental caries.

The DST count and the Snyder test were positive in some instances much earlier than the tomato agar count, perhaps indicating a slightly greater efficiency of the acidogenic tests in anticipating the onset of caries.

A few puzzling cases were found in which caries developed in the apparent absence of lactobacilli. It is suggested that counts of lactobacilli in bacterial plaques should be made in such cases as these.