Papers by Author: Teruo Asaoka

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Authors: N. Koide, K. Suzuki, M. Tsuda, Teruo Asaoka
Abstract: Due to the merits of zirconia ceramics such as high strength, toughness, and abrasion resistance, as well as chemical stability in vivo, yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) are currently used in the femoral head of hip prostheses. However, this material has a limited range of use because it is a bioinert material that does not interact with bone tissue and thus does not easily integrate directly with bone. Therefore, addition of a material surface that enables the in vivo formation of a bone-like apatite layer that exhibits bioactivity and facilitates interactions and integration with bone tissue is desired. In addition, by developing a surface structure that enhances mechanical bonding, this material can be expected to be used as an alternative aggregate under load bearing conditions. In the present study, structural design of the material surface, addition of bioactivity using reagents treatment, confirmation of formation of the apatite layer using immersion in simulated body fluid, mechanical assessment, and wettability testing were conducted with the objective of controlling interactions between zirconia ceramics and the body.
139
Authors: A. Tamura, Teruo Asaoka, K. Furukawa, T. Ushida, T. Tateishi
Abstract: α-TCP/HAp functionally graded porous beads were prepared for use as a scaffold for bone regeneration. In this research, porous beads which have compositionally graded layer, from TCP of inner area to HAp of surface area, were fabricated. It is known that the dissolution rate of TCP is fast in compare with that of HAp in living body, thus the inner area would dissolve prior to the surface area. These beads to allow the penetration of cells and blood vessel into the inner area of beads following new bone regeneration. At present, conditions to fabricate the functionally graded porous beads have been established already, and experiments using cells [MC3T3-E1] are in progress.
63
Authors: H. Sakai, Teruo Asaoka
Abstract: Due to the merits of zirconia ceramics such as high strength, toughness, abrasion resistance, and chemical stability in vivo, yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) are currently used in the femoral head of hip prostheses. However, this material has a limited applications range because it is a bioinert material that does not interact with bone tissue and thus does not easily integrate directly in the bone. Therefore, we need to add different material’s layer which enables in vivo formation of bone-like apatite layer that exhibits bioactivity , composite compound bioactive ceramics, and facilitates interactions and integration in bone tissue. In addition, by developing a surface structure that enhances mechanical bonding, this material can be expected to be used as an alternative aggregate under load bearing conditions. In the present study, various method were carried out with the objective of controlling interactions between zirconia ceramics and the body such as structural design of the material surface, addition of bioactivity using reagents treatment, confirmation of formation of the apatite layer using immersion in simulated body fluid, wettability testing and develop structure with mechanical properties equal to bone strength.
17
Authors: T. Fujii, Teruo Asaoka
Abstract: When problems with the spine of the human body occur, symptoms such as pain and numbness arise, causing impediments to everyday life. In addition, when these symptoms are severe, surgery is required. In recent years, the number of spinal operations performed has tended to increase, and accordingly, there has been an increase in the number of the spinal spacers used in fusion surgeries.In this study, we focused on zirconia as a spacer material because it is superior in terms of strength, toughness, and frictional wear characteristics and does not cause a foreign body response such as metal allergy. Therefore, our purpose was to make adjustments for mechanical characteristics that were suitable for use in spacers by combining a dense structure of zirconia with a porous structure. A further purpose was to fabricate a spinal spacer capable of strong, direct bonding with vertebrae. During the fabrication we packed a powdered mixture of zirconia powder and carbon, the source of the pores, and sintered this using a spark plasma sintering method. Thereafter, the source of the pores was eliminated by heating, and bioactivity was provided by immersion in an aqueous solution of NaOH. Observations and analysis made using a scanning electron microscope (SEM), energy dispersive X-ray spectrometry (EDS), and X-ray diffraction (XRD) allowed us to fabricate materials suitable for our purposes. We are reporting this method as well as the stress occurring at the interface of the layers.
136
Authors: Kousei Kumagai, Teruo Asaoka, Katsuko Furukawa, T. Ushida
Abstract: Recently, regenerative medicine attracts very wide attention. Regenerative medicine is a method of medical care for the purpose of recovery of the lost human organic function, resulted by an accident or diseases. It is considered that there are three important factors in the regenerative medicine, cell, scaffold and cell growth factor. In this research, the talyor made stereolithography method was used to fabricate a highly precise biodegradable scaffold which is suited for individual bone defect part. The sterolithograph, one of rapid prototyping methods, is a method of modeling by using optical hardening resin irradiated by ultraviolet laser. We have used the optical hardening resin by mixing biodegradable β-tcp as the bone formation material. At present, confirmation of detailed fabrication conditions of stereolithography are in proceeding. Experiments by using osteoblasts cells are intended.
70
Authors: Shunsuke Saito, Y. Oyake, Teruo Asaoka
Abstract: In the event of a significant injury, human bone must be repaired by artificial means. In the present study, we used titanium (Ti) to create a scaffold for cell renewal with an emphasis on strength. Because scaffolds for cell renewal require a microporous structure that enables supply of oxygen and nutrients, sintered Ti fiber was used. However, although titanium has a high fracture toughness, it does not bind to hydroxyapatite (HAp), the main component of bone, and thus requires addition of bioactivity. Following treatment by sodium hydroxide, titanium fibers were heated and immersed in simulated body fluid. Through this process, HAp was formed on the titanium surface to create a bioactive material with both a high strength and biocompatibility. Following approximately two weeks of immersion in simulated body fluid, HAp was formed such that it covered the surroundings of titanium fibers without any gaps. In addition, the fracture condition of HAp was analyzed by conducting mechanical tests, such as tensile strength and compression tests, on the titanium fibers on which HAp was formed. Furthermore, collagen coating was performed on the titanium surface, and the material was immersed in simulated body fluid to investigate and compare HAp formation.
131
Authors: Yuji Kajihata, Teruo Asaoka, Katsuko S. Furukawa, Takashi Ushida, T. Tateishi
Abstract: HAp (Hydroxyapatite) and α-TCP (alpha tribasic calcium phosphate) are non-toxic to human cells and, thus, have been studied for applications as biomaterials. HAp is a bioactive material that is not readily absorbed by the body; it offers both high strength and better tissueadhesive properties than α-TCP. In contrast, α-TCP is highly bioabsorbable; it is quickly absorbed by the body, and, therefore, for example, disappears before bone is completely replaced. If porous beads could be fabricated that would take advantage of the useful properties of α-TCP and HAp, they could be used as excellent scaffolds for cultivating cells. In the present study, ceramic beads with α-TCP at the center were fabricated and coated with a functionally graded film of HAp. A scaffold based on this configuration would be expected to have the following characteristics: good cell adhesion; strong beads; and a rate of absorption into the body that would be easy to control. In addition, to accelerate the formation of porous structure, some acid solutions were used to dissolve the beads surface layer and to penetrate pores toward inside of the bead. HAp formation through hydrolytic reaction seemed to be promoted by these acid solutions.
135
Authors: Masaki Kondo, Teruo Asaoka
Abstract: Photocatalytic titanium dioxide (TiO2) filter was prepared by hydrothermal treatment in NaOH (8M) at 80°C followed by ion exchange in HCl (0.1M), and calcination at 400°C from Ti non-woven fabric (NIKKO TECHNO, Ltd.). Ti non-woven fabric is made of metallic Ti fibers. The surface area of the fabric is several times larger than flat Ti plate, so the TiO2 filter prepared from it should have high degradation ability of organic pollutants by photocatalyst. And we thought it could be applied for the filter to purify air or water. The sample was investigated by scanning electron microscope (SEM), and energy dispersive x-ray spectrometer (EDS). The photocatalytic activity of the sample was evaluated by degradation of methylene blue (MB) solution. The change of concentration of MB solution was measured by ultraviolet visible spectrometer (UV-vis). After the hydrothermal treatment, micro network structure layer was formed on the surface of Ti. The structure was maintained after heat treatment. The elements of the layer after heat treatment were Ti and O. The sample exhibited the degradation ability of MB solution. We tried to hybridize of the TiO2 filter and hydroxy apatite (HAp : Ca10(PO4)6(OH2) ) to improve degradation efficiency by adsorption ability of HAp. The hybrid material of them were prepared by soaking the TiO2 filter into simulated body fluid (SBF) at 37.5°C for 1~7d. Then, HAp particles were formed on the surface of the TiO2 filter. But the degradation ability was lower than non-hybrid sample.
793
Authors: Teruo Asaoka, Yuji Kajihata, Katsuko Furukawa, Takashi Ushida, Tetsuya Tateishi
Abstract: As excellent scaffolds for cultivating bone cells, porous beads of bioactive ceramics such as HAp, TCP are considered to be promising. HAp and α-TCP are well known as non-toxic bioceramics to human cells, but their behavior in living body fluid are different. HAp is bioactive material which has both high strength and better tissue-adhesive properties, but that is not readily absorbed by the human body. On the contrary, α-TCP is highly bioabsorbable; it is quickly absorbed by the body, and, therefore, disappears before bone is completely replaced. To realize a composite which has suitable solubility in living body fluid, α-TCP/ HAp functionally graded porous beads were fabricated by the method of spheroidization in liquid nitrogen. This type of composite maintains the function of scaffold with sufficient strength up to growth of new bone, and after the growth, it is expected to absorbed completely in the body. In the present study, ceramic beads with α-TCP at the center were fabricated and coated with a functionally graded layer of HAp. By controlling the thickness of HAp layer, which could be realized by changing time of hydrolytic reaction, the absorption rate into the body would be easily controlled. In addition, to accelerate the formation of porous structure, some acid solutions were used to dissolve the beads surface and to penetrate pores toward inside of the beads. Observed surface and inner structure by SEM, also the measured change in absorption rate will be presented.
2021
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