Papers by Author: Masami Hashimoto

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Authors: Koji Goto, Masami Hashimoto, Hiroaki Takadama, Jiro Tamura, Shunsuke Fujibayashi, Shin Hasegawa, Keiichi Kawanabe, Tadashi Kokubo, Takashi Nakamura
Abstract: Three types of polymethylmethacrylate (PMMA)-based composite cements containing 40− 56 wt% micron-sized titania (titanium oxide) particles, designated ST2-40c, ST2-50c, and ST2-56c, were developed as bone substitutes for vertebroplasty, and evaluated for their mechanical, setting, and biological properties. In animal experiments, ST2-50c and ST2-56c were implanted into rat tibiae and solidified in situ. Their biological properties were evaluated at 6 and 12 weeks after implantation. Compressive strength, bending strength, and bending modulus increased with increasing titania content. Peak temperature during the setting reaction decreased as the filler content increased. ST2-56c had direct contact with bone over larger areas than ST2-50c at 6 and 12 weeks. Data from the present study indicated that ST2-56c is a good candidate as a bone substitute for vertebroplasty.
Authors: Masami Hashimoto, Hiroaki Takadama, Mineo Mizuno, Tadashi Kokubo, Koji Goto, Takashi Nakamura
Abstract: Bioactive bone cement with mechanical properties higher than that of commercial polymethylmethacrylate (PMMA) bone cement are strongly desired to be developed. In the present study, PMMA-based cement incorporated with nano-sized rutile particles was prepared. The PMMA-based cement (rutile content was 50 wt%) shows the compressive strength (136 MPa) higher than that of commercial PMMA bone cement (88 MPa). The hardened cement formed apatite on the surface in a simulated body fluid within 3 days. Therefore, this PMMA-based cement incorporated with rutile particles might be useful as cement for fixation of prostheses as well as self-setting bone substitutes, because of its high apatite forming ability and mechanical strength.
Authors: Masami Hashimoto, Satoshi Kitaoka, Yoshihiro Obata, Shunsuke Muto, Takafumi Ogawa, Maiko Furuya, Hiroyasu Kanetaka
Abstract: The surface potential of the TiO2 scale formed on Ti was controlled by varying the Ti heat treatment conditions in a N2 atmosphere containing a trace amount of O2. The surface potential was attributed to the effective charge of nitrogen-related defects in the TiO2, where the positive and negative surface charges were associated with (N2)0+2 and (NO)0-1, respectively. The latter defects were formed only during the early stages of the heat treatment, and with increasing treatment time, this was followed by the formation of voids containing N2 in the scale rather than the disappearance of the defects in the TiO2 crystal lattice, resulting in zero surface charge. Hydroxyapatite (HAp) formation and osteoconductivity were enhanced on nitrogen-doped TiO2 scale with either a positive or negative surface potential. In contrast, for the unchanged TiO2 scale, no HAp formation was observed and the osteoconductivity was low.
Authors: Hiroaki Takadama, Masami Hashimoto, Yorinobu Takigawa, Mineo Mizuno, Tadashi Kokubo
Authors: Jun Akiyama, Masami Hashimoto, Hiroaki Takadama, Fukue Nagata, Yoshiyuki Yokogawa, Kensuke Sassa, Kazuhiko Iwai, Shigeo Asai
Abstract: A high magnetic field is a useful tool to control the crystal alignment of non-magnetic materials such as ceramics and polymers. In the case of Hydroxyapatite crystal, the a,b-axis is aligned parallel to the direction of an imposed magnetic field. This fact implies that the alignment of the c-axis is not controllable only using a high static magnetic field due to the freedom of the c-axis in a plane perpendicular to a magnetic field direction. In this study, a high static magnetic field and mold rotation was simultaneously so applied during a slip casting process as to align the c-axis of HAp poly crystals.
Authors: Jumpei Hayashi, Kawashita Masakazu, Toshiki Miyazaki, Tada Aki Kudo, Hiroyasu Kanetaka, Masami Hashimoto
Abstract: MC3T3-E1 cell responses, such as cell adhesion and proliferation, to original and bovine serum albumin (BSA) coated disc (original-disc, BSA-disc) of hydroxyapatite (HA) or alpha-type alumina (α-Al2O3) was studied. There was no significant difference in the cell proliferation between BSA-discs and original-discs even after incubated for 14 days, but the cell number at day 14 tended to be higher (p = 0.054) on the BSA-discs of HA than on the original-discs of HA. Incidentally, the amount of adsorbed protein was higher on BSA-discs than on original-discs only until incubated in culture medium for 3 h. BSA adsorption might influence the MC3T3-E1 cell adhesion to HA, as a result the specific adsorption of albumin on HA is likely to affect the expression of the osteoconductivity of materials.
Authors: Hiroaki Takadama, Masami Hashimoto, Y. Takigawa, Masataka Mizuno, Yoshiyuki Yasutomi, Tadashi Kokubo
Authors: Paul Hideo Shingu, Keiichi N. Ishihara, Akira Otsuki, Masami Hashimoto, N. Hasegawa, I. Daigo, B. Huang
Authors: Koji Goto, Masami Hashimoto, Shunsuke Fujibayashi, Tadashi Kokubo, Takashi Nakamura
Abstract: Two types of new bioactive polymethylmethacrylate (PMMA)-based bone cements containing nano−sized titania (TiO2) particles were prepared and evaluated to assess the effect of TiO2 content on their mechanical properties and osteoconductivity. We prepared two types of bioactive bone cement, ST50c and ST60c, which contained 50 wt% silanized TiO2 and 60 wt% silanized TiO2, respectively. Commercially available PMMA cement (PMMAc) was used as a control. The cements were inserted into rat tibiae and solidified in situ. After 6 and 12 weeks, they were taken out for evaluation of osteoconductivity by scanning electron microscopy (SEM), contact microradiography (CMR) and Giemsa surface staining. SEM revealed that ST60c and ST50c apposed to bone directly while PMMAc did not. The affinity index of ST60c was significantly higher than for the other cements at each time interval. The results showed that ST60c was a promising material, but its mechanical strength should be improved before application in prosthesis fixation.
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