[Ultrastructural study of bacterial plaques from caries-free human subjects (author's transl)].

Bacterial plaques from the teeth of individuals without caries were prepared for examination under the electron microscope (Ryter and Kellenberger's fixation). Microbial polymorphism within bacterial plaques has previously been usually studied in relation to the age of the plaque. Actually, the presence of polymorphous micro-organisms and variations in microbial density observed in 48 hours old plaques, must be related to other factors. Micro-organisms of the same type, as well as bacteria of different types which adhere together, reveal symbiosis and a competition process within the bacterial plaque, thus leading to changes in metabolism and lysis of many of the bacteria. Disturbances in bacterial cell walls; septal vesicular formation and intracellular structures are observed. Bacteriophages found in the plaques may be the cause of lysis of bacteria. Disturbances in bacterial metabolism could explain the lack of carcinogenicity of micro-organisms, and bacterial antigenic complexes which induce probably useful immunological reactions in the host are revealed by the lack of dental caries.