A scanning electron microscopic study of the relationship between the most apically located subgingival plaque and the epithelial attachment.

Twelve teeth with chronic periodontitis were extracted and examined in the scanning electron microscope. Subgingival plaque in deep pockets was usually covered by a surface coating, which was absent in the apical part. The apical plaque displayed an organized structure, although varying form one tooth to another. The microorganisms were sometimes overlapping the epithelial cell remnants. Coccal forms were seldom found, but on a morphologic basis, rod-like, filamentous, spiral and branching forms were identified. Both bacteria and spirochetes seemed to have the capacity to invade the epithelial remnants on the tooth surface. The epithelium in direct contact with the microorganimsm showed a widening of the intercellular spaces and a change in surface morphology. This was in contrast to cell layers more distant from the plaque, which appeared normal and homogeneous. Similar reactions were also seen in gingival epithelial-like cell cultures infected with plaque of human origin.