Basic Study on the Relationship Between Remodeling of Periodontal Tissue and Mastication -Effects of Mechanical Force on Cytokins Synthesis of the Cells Derived from Periodontal Ligament-

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Periodontal ligament may play an important role on tooth eruption, development of root, and root resorption. The tissue physiologically receives mechanical force during mastication. We focused on the effects of the intermittent mechanical strain on the growht and cytokine synthesis of periodontal ligament (PDL) fibroblasts in vitro. The cells were derived from human periodontal ligament of permanent teeth (PDL-P) and deciduous teeth (PDL-D) according to the method of Kawase (Adv.Dent.Res.2 : 234-239,1988). The two kind of PDL cells were cultured in flexible bottomed culture plates. The cells were mechanically stretched at 50,000micro Strain (5% elongation), 3cycles/minute for 24 hours on the day 3 or day 6 in culture using Flexercell Vacuum System. After the stretching we measured DNA content and alkaline phosphatase activity of the cell layr, macrophage colony stimulating factor (M-CSF) and transforming growth factor beta 1 (TGF-beta1) contents in the conditioned medium. TGF-beta1 level in the conditioned medium of PDL-P was significantly higher than that of PDL-D (2 to 3 fold higher) and it was stimulated (20 to 30%, p<0.01) by the mechanical stretching in the end of growth phase (on the day 7). M-CSF secretion of PDL-D was significantly higher (1.3 to 1.8 fold) than that of PDL-P and it was inhibited (-20%, p<0.01) by the mechanical stretching at the end of growth phase (on the day 7). These data suggest that periodontal ligament cells synthesize and secrete the factors that affect bone remodeling and root resorption and the level of those factors change in response to mechanical stress.