Mechanism and prevention of periodontal pocket formation

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The purposes of this research project were to establish rat model of periodontal pocket formation, to clarifymechanism of pocket formation, and to evaluate effects of mechanical stimulation of gingiva on healing of periodontal pocket.In the year 2001, rat model of periodontal pocket formation was established with application of lipopolysaccharide and bacterial proteases into gingival sulcus. Apical migration of junctional epithelium along the root surface and apoptosis of periodontal ligament fibroblast were followed by promoted proliferative activity of junctional epithelium and collagen destruction at the initiation of periodontal pocket formation.In the year 2002, optimal duration of mechanical stimulation to promote cell proliferation in normal gingiva was determined. Optimal duration of mechanical stimulation to promote proliferation of junctional epithelial cells and fibroblasts were 10 or 20 seconds and 5 or 10 seconds, respectively.In the year 2003, effects of mechanical stimulation on healing of periodontal pocket were evaluated using the rat pocket formation model established in the year 2001 and duration of stimulation determined in the year 2002. Mechanical stimulation reduced number of polymorphonuclear leukocytes in both junctional epithelium and connective tissue, and reduced area of destroyed collagen fibers.In the year 2004, effects of mechanical stimulation on cell cycle of normal gingiva were evaluated using proliferating cell nuclear antigen(PCNA) and bromodeoxyuridine(BrdU). Mechanical stimulation increased both numbers of PCNA- and BrdU-positive cells in junctional epithelial cells and fibroblasts. The results suggest that mechanical stimulation enhances DNA synthesis of junctional epithelial cells and fibroblasts.The results of this project contribute to develop effective periodontal treatment using activation of host defense by mechanical stimulation of gingiva.