Papers by Author: Hiroshi Nakada

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Authors: Hiroshi Nakada, Toshiro Sakae, Mari Teranishi, Takao Kato, Takehiro Watanabe, Takahiro Takahashi, Yasuhiko Kawai, Racquel Z. LeGeros
Abstract: Ovariectomized rats were fed a diet containing minerals at high concentrations, such as Ca, P, and F (high-mineral diet), and changes in the femoral diaphysis were investigated after 24 weeks. The femur was mainly red and partially orange on the color scale of the 3D-map in Groups A and B, showing a high BMD. The region adjacent to the marrow cavity was yellow, showing a lower BMD than that in the outer region of the femur. In Group C, the red area was small in the outer region and the inner region was mainly yellow and green on the color scale. The inner region adjacent to the marrow cavity showed a view of unevenly resorbed bone, and the BMD was lower than those in Groups A and B. Incorporation of F into the body influences the apatite crystal structure and crystal growth, which subsequently influences adsorption of F to crystals and structural changes. Therefore, it is important to ingest F at the optimum concentration.
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Authors: Toshiro Sakae, Hiroshi Nakada, Mari Teranishi, Takao Kato, Shizuka Suzuki, Akira Yanagawa, Norio Yasuda, Shukichi Ochiai, Nobby Kitagawa, Yasuhiko Kawai, Racquel Z. LeGeros
Abstract: Differences in structural and crystallinity between the lateral and medial regions of the central femoral diaphysis in low-mineral-diet-fed ovariectomized rats were investigated using polarization microscopy and Raman spectral analysis. Eighteen 19-week-old female Wistar rats were divided into 3 groups (Group 1: sham ovariectomy + normal diet group, Group 2: ovariectomy + normal diet group, Group 3: ovariectomy + low-mineral-diet group). Measurements were performed in the lateral and medial regions of the femoral sagittal cross-section at 24 weeks of feeding. On polarization microscopy, tubular structures of haversian and Volkmanns canals and osteocytes were observed in the femur in Groups 1 and 2. In Group 3, the number of these tubular structures in the femur was decreased compared to those in Groups 1 and 2. Moreover, the bone width of the femur decreased in Group 3 compared to those in Groups 1 and 2. On Raman spectral analysis, the peaks of organic and inorganic components were observed in the lateral and medial regions of the femur in all groups. In magnified views of the peak of ν1PO43-spectrum, the peaks in the lateral and medial regions overlapped in Group 1, but the peak of the medial region was about 0.3 and 0.8 cm-1 shifted toward the low wavenumber side compared to those of the lateral region in Groups 2 and 3, respectively. Based on these findings, the influences of reduced estrogen secretion and the low-mineral diet were clarified as differences in the femoral structural and crystallinity on polarization microscopy and Raman spectral analysis. Since highly sensitive detailed point analysis can be performed within a short time using Raman spectral analysis, it may be useful for high-dimensional structural analysis.
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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: Hiroshi Nakada, Toshiro Sakae, Taketoshi Suwa, Racquel Z. LeGeros, Atsuko Gunji, Takao Kato, Kihei Kobayashi
Abstract: The purpose of this study is to determine the potential of the LEBRA-PXR imaging in investigating the details of newly formed bone around the dental implants. Transmission image observation of the undecalcified specimen at the wavelength of 1.771 Å showed clearly the formation of immaturely calcified new bone around the dental implants which could not be observed in the usual CMR nor conventional X-ray imaging apparatus.
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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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Authors: Taketoshi Suwa, Toshiro Sakae, Hiroshi Nakada, Racquel Z. LeGeros, Kihei Kobayashi
Abstract: Our studies previously demonstrated that new bone formed around implants can be classified into 3 or 4 types based on tissue structure and composition. Results of the present study, using polarized light microscopy, and microscopic Fourier transform infrared spectroscopic imaging (micro-FT-IR) and micro-XRD to examine different areas in the peri-implant new bone, suggest differences in crystallinity (crystal size) between pre-existing bone and peri-implant new bone.
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