[Studies on the relationship between dental plaque and the hard tissues of healthy and diseased teeth]

1. Dental plaques were detected in all the teeth under investigation, with the exception of impacted teeth. 2. The appearance of the plaques is regular. They occur chiefly in certain zones of the tooth crown and in retention areas. The film thickness ranges from 10 to 60 mum. 3. No alterations of the structure or of the primary texture of the hard tissues were observed on healthy and periodontally diseased teeth. The plaques infiltrate but slightly into the surface. 4. Carious teeth have a different appearance. The plaques infiltrate more or less deeply. They even penetrate into the macroscopically free zones of the enamel as well as of the dentine. The infiltrate is diffuse, especially in regions where the relationship between mineral and organic constituents is distrubed.