Bacterial plaques occur alike over carious and non-carious areas on human teeth. Neither physical nor morphological differences in carious or non- carious plaques could be detected in ground sections.
Study of the morphology of several thousand smears suggests that it was possible to determine presence or absence of an active carious process in the areas from which the plaques were taken. For this purpose plaques were removed from teeth, in situ, and smeared on sterile coverslips. Before fixation, plaque material was transferred from the coverslip to a tube of Jay’s medium. The resultant cultures gave growths of lactobacilli in a very high percentage of the smears considered positive for caries on the morphological basis. Most of the smears considered negative on this basis were negative for lactobacilli when cultured. The method is of value as a diagnostic aid. The smears, either positive or negative, contain many organisms which apparently do not grow on the artificial media usually employed in routine laboratory work.
Reference: J. Den,. Res., 15, 326, 1936.