Light and Electron Microscopic Studies of experimentally-induced Pathologic Changes in the Rat Periodontal Tissue

¹ Department of Oral Pathology, Hiroshima University School of Dentistry, 1-2-3 Kasumi, Minamiku, Hiroshima 734, Japan

Morphological changes in periodontal tissues following topical application of lipopolysaccharide (LPS) or prostaglandin E₂ (PGE₂) were examined in Wistar rats by light and electron microscopy. Ultrastructural demonstration of acid phosphatase and immunohistochemical localization of lysozyme in these tissues were also studied. The number of osteoclasts along the alveolar bone facing the periodontal ligament was counted.

After topical application of LPS, degeneration and necrosis of the junctional epithelial cells, gingival fibroblasts, and alveolar osteoblasts were observed, as were increased bone resorption by osteoclasts and enhanced phagocytosis of collagen fibrils by fibroblasts. LPS appears to traverse easily through the junctional epithelium into the underlying gingival connective tissues. There it can cause destruction of deeper periodontal tissues by activating alveolar bone resorption and by enhancing the phagocytosis of collagen fibrils. PGE₂ topically applied induced similar morphological changes. Possible participation of PGE₂ in the induction of these LPS-related changes is discussed.