Papers by Author: T. Akazawa

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Authors: Junichi Tazaki, S. Yodogawa, Masaru Murata, K. Ito, T. Akazawa, J. Hino, Md.A. Kabir, H. Nagayasu, M. Arisue, T. Shibata, T. Hanawa
Abstract: Our approach to the design of biological material scaffolds for bone regeneration is the creation of cell environments that mimic natural tissues. Recently, we confirmed hitologically that the material surfaces of conventional, nonabsorbable ceramics shed body fluid. For bone engineering, it is known that ideal scaffolds should be bioabsorbable, mimetic, and hydrophilic materials that allow for the permeation of liquid components, such as blood and/or extracellular fluid. In our previous study showed functionally graded hydroxyapatite (fg-HAp) absorbed body fluid including albumin. In this study, we investigated the behavior of human blood adsorption to the fg-HAp by using the scanning electron microscope (SEM). The adsorption of the platelets and the formation of the fibrinous network were observed in the fg-HAp group incubated 20 minutes.
Authors: K. Ito, Masaru Murata, J. Hino, Junichi Tazaki, T. Akazawa, M. Arisue
Abstract: Body fluid permeability and blood compatibility of biomaterials are especially critical properties for regenerative bone therapy [1, 2]. To have a role in bone repair, biomaterials must have the adsorptive performance of various bone growth factors. The bone-inductive property of rabbit dentin was discovered in 1967 [3]. In our previous study, we have been researching the autograft of human demineralized dentin matrices (DDM) as a clinical study [4]. DDM is an acid-insoluble collagenous material. On the other hand, hydroxyapatite (HAp) is a mineralized material. Commercially available HAp block (APACERAM-AX®, 85%-porosity with micropore) has been used as the artificial biomaterial in bone therapy [5]. Bone morphogenetic proteins (BMPs) are the strong hard tissue-inducing factors [6]. In this study, we investigated the existence of BMP-2 and -7, among proteins adsorbed to DDM and HAp, using immunoblottong analyses. The DDM granules and HAp blocks (64mm3) were implanted subcutaneously in 8-week-old Wistar rats, and sacrificed at 2 days after the implantation. Explanted DDM and HAp were homogenized by the ultrasonic procedure in phosphate-buffered saline (PBS) and the adsorbed proteins were separated on a 5-20% sodium dodecyl sulphate (SDS) polyacrylamide gradient gel by electrophoresis. For Western blotting, proteins in the gel were transferred to a polyvinylidene difluoride membrane and detected by anti-BMP-2 monoclonal antibody and anti-BMP-7 monoclonal antibody. BMP-2 and BMP-7 were detected as a major band at 50 kDa among proteins collected from the in vivo implanted DDM and HAp. BMP-2 was detected the second major band at 125 kDa in HAp and both BMP-2 and BMP-7 were detected the some minor bands in DDM and HAp. The bands of BMP-2 were stronger than those of BMP-7 in all. The DDM and HAp adsorbed BMP-2 and BMP-7. These results indicate that DDM is a useful bone substitute as much as HAp, adsorbed to the bone-inducing factors, in the bone engineering field.
Authors: Masaru Murata, T. Akazawa, J. Hino, J. Tazaki, K. Ito, M. Fujii, T. Shibata, M. Arisue
Abstract: Bone and dentin consist of hydroxyapatite, collagen and body fluid. From biological points of view, we have been focusing on HAp and collagen materials for bone regeneration. The aim of this study is to estimate the appearance of multinuclear giant cells for non-organic (functionally graded HAp: fg-HAp) and organic materials (demineralized dentin matrix: DDM), histologically. The fg-HAp ceramic: Biomimetic fg-HAp was designed by using the partial dissolution-precipitation methods. The fg-HAp with micro-pores of 10-160 nm had larger specific surface areas (30-40 m2・g-1) than the synthetic HAp. Acid- insoluble dentin matrix (DDM): Human teeth were crushed under the cooling, completely demineralized in 0.026N HNO3 solution, and dried. The materials were implanted into the subcutaneous tissues (Wistar rats, 4 week-old, male), and removed at 1 and 4 weeks after the operations. Multinucleated giant cells were counted in the H-E sections. Giant cells predominantly appeared on the biodegradable micro-crystals at 1 week. The number of giant cells was more numerous in fg-HAp than in DDM. There was a significant difference in the cell number between fg-HAp and DDM. The absorption mechanism of fg-HAp should be predominantly cellular phagocytosis, while that of DDM might be predominantly enzymatic digestion. These data support the hypothesis that the biological HAp crystals may function as mineral signal in the recruitment and differentiation of multinucleated giant cells.
Authors: Junichi Tazaki, Masaru Murata, Y. Nakanishi, M. Ochi, Y. Hirose, T. Akazawa, S. Yodogawa, J. Hino, K. Ito, H. Kitajo, M. Arisue, T. Shibata
Abstract: In our previous clinical study, autogenous demineralized dentin matrices (DDM) prepared from the functional vital teeth (#38, #41) of thirty-five-year-old female were grafted on the bone defect, using newly developed mill, and then received to the host without troubles. In this study, we implanted the human tooth dentin adjusted previously and the dental implants into the regions of missing tooth simultaneously. Fifty-seven-year-old female presented with missing teeth (#35-#37, #45-#47). First, a non-functional vital tooth (#18) were extracted and cryopreserved immediately. 11 months after extraction, the tooth was crushed by newly developed auto-crash mill using ZrO2 vessel and ZrO2 blade for 1 minute. The crushed granules were demineralized completely in 2% HNO3 solution, rinsed in cold distilled water and lyophilized (granule size: 0.5-2.0mm). The bacteria-free of the DDM were confirmed by the bacteriological examination before use. Drilling of the prospective implant beds were then performed according to the manufacture’s protocol and a screw-type rough surface implants (Nobel Biocare® Mk III) were placed. The adjusted DDM granules were implanted into the bone defect (#45). There are no postoperative complications at 3 years after implantation. This case indicates that the preserved autogenous DDM can be used as collagenous biomaterials with osteoinductive potency.
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