Papers by Author: Keita Uetsuki

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Authors: Satoshi Hayakawa, Keita Uetsuki, Akinori Kochi, Yuki Shirosaki, Akiyoshi Osaka
Abstract: A recently developed “GRAPE® technology” provides titanium or titanium alloy implants with spontaneous apatite-forming ability in vitro, which requires properly designed gaps and optimum heat treatment in air. In this study, pure titanium pieces were thermally oxidized in air and pre-irradiated by UV-light under different environmental conditions such as in air or in ultra-pure water before aligning pairs of specimens in the GRAPE® set-up, i.e., two pieces of titanium substrates were aligned parallel to each other with optimum gap width (spatial design). Then, they were soaked in Kokubo’s simulated body fluid (SBF, pH7.4, 36.5°C) for 1-2 days to clarify how the UV-light pre-irradiation affects the in vitro apatite nucleation on the substrates under the specific spatial design. UV-light pre-irradiation in water led to the deposition of a large number of apatite particles within 1 day, and showed apatite X-ray diffraction, although UV-light pre-irradiation in air and non-pretreated specimens gave the deposition of a few apatite particles and did not show any apatite X-ray diffraction. These results indicated that the rate of primary heterogeneous nucleation of apatite increased by UV-light pre-irradiation in ultra-pure water. TF-XRD patterns of the surface of the substrates thermally oxidized in air at 500°C showed the peak at 2θ = 27º assignable to the 110 diffraction of rutile phase of titanium dioxide (ICDD-JCPDS data #21-1276). Previous studies reported that the primary heterogeneous nucleation must be induced by Ti-OH groups on titanium oxide layer. Probably, the UV-light pre-irradiation in ultra-pure water can increase the number of Ti-OH groups on the surface, resulting in accelerated primary heterogeneous nucleation of apatite.
Authors: Atsushi Sugino, Keita Uetsuki, Kanji Tsuru, Satoshi Hayakawa, Chikara Ohtsuki, Akiyoshi Osaka
Abstract: Apatite formation on the surface of materials in body environment is an essential condition to show osteoconduction after implantation in bony defects. This study reports the novel technique for providing the apatite-forming ability to titanium metals by only controlling the spatial gap and thermal oxidation. Two pieces of titanium thermally oxidized at 400 °C were set together like V-letter with varied mouth opening. They showed the formation of apatite on both facing surface after exposure to a simulated body fluid (SBF) proposed by Kokubo and his colleagues, when the gap was less than approximately 600 μm. Moreover, specimens with micro-grooves of 500 μm in depth and 200-1000 μm in width was able to form apatite in SBF with in 7 days, after they were thermally oxidized at 400 oC. These results indicated that the titanium metals were provided with apatite-forming ability, i.e. osteoconduction, due to controlled gap with thermally oxidized surface. Hence, we conclude that bioactive titanium substrate showing osteoconduction can be produced by designed machining followed by thermal oxidation at an appropriate temperature.
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