Papers by Author: Yasuko Numata

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Authors: Hiroshi Nakada, Yasuko Numata, Taketoshi Suwa, Y. Okazaki, Racquel Z. LeGeros, Toshiro Sakae, Takao Kato, K. Kuwahara, Kihei Kobayashi
Abstract: We have developed a new Ti alloy, Ti-15%Zr-4%Nb-4%Ta alloy (Ti-15-4-4) that showed higher biological safety and mechanical properties than the currently used Ti-6%Al-4%V alloy. The purpose of this study is to determine the biological performance of the new alloy. Ti-15-4-4 implants (machined or blasted) were placed in surgically created defects in rabbit femurs. The rabbits were sacrificed after 4, 8, 16, 24 and 48 weeks. Bone mineral density (BMD) and area of newly formed bone around the implants were measured using micro-CT. Results showed that the Ti-15-4-4 alloy is biocompatible and forms new bone around the Ti-15-4-4 implant, regardless of the surface treatment. The BMD and area of newly formed bone around the blasted implant surfaces were significantly greater than those around the machined surfaces. These results indicate that the new Ti-15-4-4 alloy has a potential for use as implants and has the advantage of improved mechanical properties described in earlier studies.
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Authors: Yasuko Numata, Toshiro Sakae, Taketoshi Suwa, Hiroshi Nakada, Racquel Z. LeGeros, Kihei Kobayashi
Abstract: The purpose of this study was to evaluate synthetic calcium phosphates and animal bones using Raman spectroscopy and explore the possibility of its application in characterizing newly formed bone around implants. Synthetic calcium phosphates (monobasic calcium phosphate, dibasic calcium phosphate, tribasic calcium phosphate, fiber apatite, hydroxyapatite and carbonate hydroxyapatite) and animal bones (from pig, cow, rabbit with and without implants) were analyzed in this study. Slight differences in the Raman bands among the 7 types of synthetic calcium phosphate were observed. Furthermore, a 3 cm-1 difference was noted in the bands of the main PO4 3- in rabbit’s bone formed around the implant, compared to the existing bone, suggesting a difference in the molecular structure between the existing and newly formed bones.
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Authors: Taketoshi Suwa, Toshiro Sakae, Hiroshi Nakada, Yasuko Numata, Racquel Z. LeGeros, Isamu Sato
Abstract: To clarify new bone tissues, radiography with a newly developed tunable wavelength and highly parallel Parametric X-ray, PXR, was applied. Methods: PXR was generated by a LINAC at LEBRA, Nihon University (Hayakawa et al., 2005). X-ray wavelength was tuned from 7 KeV, 0.177 nm, to 16 KeV, 0.0775 nm. Coated or grit-blasted Ti-alloy implants modified with coating or blasting were implanted in surgically created defects in rabbit tibia. Undecalcified polished thin sections were prepared from the implant/bone areas 1 and 4 weeks after implantation. Results: PXR radiography showed a distinct difference between the newly formed bone and the compact bone. Color-mapping of the images showed an increase in the total amount of bone formation with time. Conclusion: Application of LEBRA-PXR, a high-powered, highly monochromatized and highly parallel oriented X-ray allowed easy and accurate radiographic analysis of new bone formation around the implant.
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