Papers by Author: Takao Kato

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.

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 ν₁PO₄^3-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.

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.

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.