| Co-Investigator(Kenkyū-buntansha) |
UO Motohiro Hokkaido University, Graduate School of Dental Medicine, Research Associate, 大学院・歯学研究科, 助手 (20242042)
OHKAWA Syoji Hokkaido University, Graduate School of Dental Medicine, Research Associate, 大学院・歯学研究科, 助手 (40001945)
KONDO Seiichiro Hokkaido University, Graduate School of Dental Medicine, Associate Professor, 大学院・歯学研究科, 助教授 (80018431)
YOKOYAMA Atsuro Hokkaido University, Graduate School of Dental Medicine, Research Associate, 大学院・歯学研究科, 助手 (20210627)
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| Research Abstract |
(I) REFRACTORY METALS : Biocompatibility was evaluated for IVA (Ti, Zr, Hf), VA (V,Nb, Ta), VIIIA (Re) group metals and others (Cu, Ag, Fe, Ni, stainless) by implantation test in rat. Metal dissolved region was visualized by supersensitive elemental mapping using XSAM (X-ray Scanning Analytical Microscope). Biocompatibility of refractory metals except V was confirmed. (II) SURFACE-NITRIDED TI : (1) Physical properties/Golden colored surface nitride layer is composed of TiN+Ti2N (Thin Film X-ray diffraction) with 2μm thickness (SEM observation of cross section) and Vickers hardness 1300. This remarkably high hardness resulted in no scratches produced even if an ultrasonic scaler used in clinical operation is applied. Rotated tribological abrasion test with constant load using an ultrasonic scaler was done for evaluation of scratch/abrasion resistance. (2) Biocompatibility/Biocompatibility of TiN was concluded approximately equivalent to Ti from quantitative analysis of direct contact ra
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tio of new bone to implant material and amount of new bone formation in animal implantation test. (3) Dental implantation test/The implant with its abutment composed of TiN was evaluated by miniature dental implantation test using mandibular molar teeth of rat. (4) Neutrophils cytotoxicity test of Ti minute abrasion powders/Soft tissue embedded with Ti powders of 10 μm and 1μm size showed inflammatory reaction even after 24 weeks. Phagocytosis of Ti particles by macrophage and change of morphology of neutrophils were observed. Cytokine TNF α was detected only for the case of 1μm Ti, which shows that the cytotoxicity also arises from physical size effect. (III) RELATED DERIVATIVE RESEARCH : (1) Functionally graded implant/Part of hydroxyapatite (HAP) suffers decomposition during sintering process of Ti/HAP functionally graded materials, while HAP is conserved without decomposition through sintering process in Ti/(HAP+TiN) system. (2) Functionally graded composite resin/To suppress the excessive stress concentration by impulsive force on upper crown part, which causes fracture in root part of tooth, when the core post is applied in residual tooth root, functionally graded composite resin with UDMA matrix and gradually changing silica filler content (0-80%) was produced by laser lithography. Stress relaxation effect was confirmed by optoelastic method and simulation using finite element method. (IV) CONCLUSION : Biocompatibility and extremely high surface hardness suggests potential applications promising where abrasion resistance is essential, such as (1) abutment part of dental implant where epithelium is penetrated through and (2) sliding surface of joints in artificial bone. Less
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