A Fundamentel Study of Mineral Trioxide Aggregate(MTA)-Biological Effects to Dental Pulp and Periodontal Tissues and Behaviours of Related Cells-

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Aim of these consecutive studies was to investigate biological effects of Mineral Trioxide Aggregate(MTA) to calcified tissue formation from in vivo and in vitro assessments.Experiment 1 : Immuno-histological assessment of new calcified tissue formation promoted by MTA on Rat experimental modelFirst of all, the in vivo study with a rat experimental model has been performed in orda to evaluate effect of MTA for new bone formation. In this study, the ability of calcified tissue formation after the implantation of MTA in a rat parietal bone. IRM(Intermediate Restorative Material) was used as a control. MTA was encapsulated by the fibrous csonnective tissue in which PCNA and Cbfa-1 positive cells with some new calcified tissue formation was immuno-histologically observed. Otherwise, IRM was also encapsulated by the fibrous connective tissue, but any calcified tissue formation and Cbfa-1 positive cells were not founded. Those phenomena suggested that MTA might induce the difierentiation of … More undifferentiated pre-osteoblastic cells to osteogenic cells and on the other hand, IRM might be a low biocompatible material.Experiment 2 : Behaviour of osteoblast-like cells on MTA associated with expression of type I collagen and bone related protein mRNAsSecondary, the in vitro study was performed to investigate a behaviour of rat bone marrow cells(RBM), osteoblast-like cells, on MTA compared with IRM. RBM obtained from rat femur and cultured were used in this study. The cultured RBM were seeded on each material, and they were evaluated morphologically using scanning(SEM) and transmission(TEM) electron microscopies. Furthermore, the calcium released hydrorated material, the cell proliferation ratio and alkaline phosphatase(ALP) activity were analyzed, and the expression of type I collagen and bone related protein mRNAs were evaluated.SEM showed that RBM attached to MTA and had a flattened appearance without nuclear protrusions and microspikes. TEM showed that the cells attached in the same manner as the control group, but gaps lager than 2 μm were frequently observed. The calcium released from hydrated MTA was about 130 ppm after 3days of immersion in saline. The ALP activity was similar to the control group. Cell proliferation and expression of type I collagen mRNA was significantry lower, while the expression of osteopontin mRNA was significantly higher than the control group at the 3^<rd> day of culture. In IRM groups, a few rounded cells were observed on the material but no living cells were seen. Less