EVANSTON DENTAL CARIES STUDY

XII. A SURVEY OF LACTOBACILLUS COUNTS WITH REFERENCE TO UNTREATED CARIOUS SURFACES BEFORE AND AFTER EXPOSURE TO FLUORIDATED WATER

¹ Zoller Memorial Dental Clinic, University of Chicago, Chicago, Ill.

The results of the study of 2,235 saliva specimens contributed by specific age group children in the Evanston Dental Caries Study in relation to lactobacillus counts and untreated dental caries rates before fluoridation and for a period of 6 years and 10 months after fluoridation have been reported.

In the younger children the negative cases of the low lactobacillus division increased from 43.75 per cent before fluoridation to 57.57 per cent after 82 months of fluoridation. The younger age group with 11.90 per cent of the lactobacillus negative cases with no carious surfaces in 1946 had 26.31 per cent in 1953. The untreated various surface rates per hundred children in the low and moderate lactobacillus divisions were considerably less in 1953 than in 1946.

In the older age group of children the negative lactobacillus cases of the low lactobacillus division increased from 39.13 per cent in 1946 to 42.63 per cent in 1952. The percentage of lactobacillus negative cases with no carious surfaces in 1946 was 5.55 per cent and 16.36 per cent in 1952. An increase of lactobacillus colony counts was noted in the older age group as in 1946, 61.60 per cent of the cases were in the low lactobacillus division while in 1952 only 46.57 per cent of the cases were found here. In 1946, 29.91 per cent of all the cases of the older children were found in the moderate lactobacillus division. In 1952, 47.65 per cent of the cases were found in this division.

The variation associated with the high lactobacillus division was attributed to the small number of cases in this division while the differences in the make-up of the control group and the study group were thought to be responsible for some of the differences in rates found in these two groups.

A relationship between the lactobacillus count and the untreated dental caries rate was noted in that the cases with low lactobacillus counts had less untreated carious surface rates than had the cases with greater lactobacillus colony counts.

It is evident from the data that shifts in the proportions of children in the high, moderate, and low lactobacillus divisions have taken place which are greater than would be expected due to chance. It is assumed that these shifts may be related to the sodium fluoride in the water supply.