Histopathological study of experimental periodontitis in rats--ultrastructures, permeability, immunohistochemistry, and morphometric analysis in both pocket and long junctional epithelial

To elucidate the biological characteristics of both pocket and long junctional epithelia in experimental periodontitis, elastic rubber was inserted between the first and second molars of the left maxilla in rats. The rubber was removed after a week. An immunohistochemical study using anti-laminin and permeability experiments using peroxidase were conducted; examinations were made of ultrastructures and lanthanum; and a morphometric analysis was made of the distribution of capillaries immediately below the epithelium. Results: 1. Periodontal pockets formed from 5 days to 2 weeks after removal of the rubber. The long junctional epithelium was appearent from the fourth week after removal. Immunohistochemical study showed that laminin was located at the internal and external basal laminae in the long junctional epithelium but not on the surface of the pocket epithelium. 2. Electron microscopy showed the pocket epithelium to consist of flattened cells aligned parallel to the tooth surface in the coronal portion. The epithelium, which included numerous vacuoles, manifested especially wide intercellular spaces in which a large number of polymorphonuclear leukocytes were evident. Bacteria surrounded by neutrophils could be seen on the surface of the cementum in the pocket. Invading neutrophils split the epithelium at the central portion of the pocket. In the apical portion, the epithelium formed spindles that adhered to the cementum by means of half-desmosomes. Many neutrophils and fenestrated capillaries were observed in connective tissue immediately below the epithelium. 3. The long junctional epithelium consisted of 2 or 3 cell layers aligned parallel to the tooth surface. Intercellular spaces in the long junctional epithelium were as wide as those in the pocket epithelium and contained a small number of lymphocytes and a few neutrophils. Half-desmosomes were detected between the epithelial cells and the cementum. From the central to the apical region, epithelial tissues assumed a knife-edge form. Desmosomes and gap junctions occurred among these cells. Dense granules containing a limiting membrane and homogeneous electron-dense material were observed int he peripheral cytoplasm. Although fibroblasts aligned parallel to the epithelium occurred in them, few collagen fibers, inflammatory cells and capillaries were to be recognized in the connective tissue. 4. Permeability experiments in the pocket and the long junctional epithelium produced analogous results. Light microscopy showed that, in both epithelia, peroxidase penetrated into intercellular spaces and leaked into the pocket. Electron microscopy showed that, as an electron-dense material, lanthanum was detected in intercellular spaces and connective tissues.(ABSTRACT TRUNCATED AT 400 WORDS)