Basic study on the effect of mastication for growth and development of dentition

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It is not clear the effect of TRAP on the cells derived from periodontal ligament that have osteoblast like characters under the condition with mechanical stress. We used the recombinant protein of TRAP(NOVUS Co. Ltd.) in this study. Osteoblasts were cultured in the stretch chambers(STREX Co. Ltd.) and loaded with cyclic mechanical stretching by cell stretch system(SIB-140). The cells were cultured for 72 hours to preconfluent phase with or without TRAP in the culture medium then stretched with 20% elongation horizontally at 40 cycles per minutes for 16 hours. The results from Real-time PCR revealed that TRAP addition decreased the mRNA level of Osterix and CBFA1 on the MC3T3 cells furthermore loading with mechanical stretch enhanced the effects. We investigated the effect of mechanical stress on mRNA expression level of RANKL and OPG. TRAP or mechanical stretching did not affect the expression level of OPG mRNA. On the other hand RANKL mRNA level increased by TRAP addition while mechanical stretching decreased the mRNA level. Mechanism of the suppression on osteoblast differentiation by TRAP and mechanical stretching. Was not clear however the effect of mechanical stretching suggested the osteoblasts in alveolar bone suppress osteoclast differentiation during tooth movement.