The Relation of Caries Activity to Lactobacillus Counts and Types and to the Fluoride Content of Drinking Water

Abstract

A follow-up examination for new caries, and number and type of lactobacilli, in the saliva was made 1 year after the preliminary examinations on 312 children aged 11 to 14 yrs. Approx. half of the group lived in Boulder, Colorado, where there is no fluoride in the drinking water, and half in Denver where there is 1 ppm. fluoride. Previous investigations had shown that a rhamnose-fermenting lactobacillus is found associated with caries more often than other types. The present expts. indicated that those drinking water containing fluoride who had large numbers of rhamnose-fermenting lactobacilli in their saliva were more likely to have increased caries the following year than those who did not have this type of lactobacillus present. When there was no fluoride in the water, nearly all of the children had increased caries, regardless of number and types of lactobacilli. The finding of large numbers of lactobacilli in the saliva, of any type, was usually associated with a rise in the number of decayed surfaces. Bacterial flora of the saliva of this age group varied considerably from one year to the next, both qualitatively and quantitatively. Fluoride in drinking water in a concentration of 1 ppm. appeared to have no effect on the type of lactobacillus which may become established.