Mori A, Ohtsuki C, Miyazaki T, Sugino A, Tanihara M, Kuramoto K, Osaka A
Nakashima Medical Division, Nakashima Propeller Co., Ltd., 688-1, Jodo-Kitagata, Okayama, 700-8691, Japan.
J Mater Sci Mater Med. 2005 Aug;16(8):713-8. doi: 10.1007/s10856-005-2607-4.
Bone cement consisting of polymethylmethacrylate (PMMA) powder and methylmethacrylate (MMA) liquid is clinically used for fixation of implants such as artificial hip joints. However, it does not show bone-bonding ability, i.e., bioactivity. The lack of bioactivity would be one of factors which cause loosening between the cement and the implant. The present authors recently showed the potential of bioactive PMMA-based bone cement through modification with gamma-methacryloxypropyltrimethoxysilane (MPS) and calcium acetate. In this study, the effects of the kinds of PMMA powder on setting time, apatite formation and compressive strength were investigated in a simulated body fluid (Kokubo solution). The cement modified with calcium acetate calcined at 220 degrees C could set within 15 min when the PMMA powder had an average molecular weight of 100,000 or less. The addition of calcium acetate calcined at 120 degrees C in the PMMA powder required a much longer period for setting. The modified cements formed an apatite layer after soaking in the Kokubo solution within 1 day for cement starting from PMMA powder with a molecular weight of 100,000 or less. Compressive strengths of the modified cements were more than 70 MPa for cements starting from 100,000 and 56,000 in molecular weight. After soaking in Kokubo solution for 7 days, the modified cement consisting of PMMA powder of 100,000 in molecular weight showed a smaller decrease in compressive strength than that consisting of 56,000 in molecular weight. These results indicate that bioactive PMMA cement can be produced with appropriate setting time and mechanical strength when PMMA powders with a suitable molecular weight are used. Such a type of design of bioactive PMMA bone cement leads to a novel development of bioactive material for bone substitutes.
由聚甲基丙烯酸甲酯（PMMA）粉末和甲基丙烯酸甲酯（MMA）液体组成的骨水泥在临床上用于固定人工髋关节等植入物。然而，它不具备骨结合能力，即生物活性。缺乏生物活性可能是导致骨水泥与植入物之间松动的因素之一。作者最近通过用γ-甲基丙烯酰氧基丙基三甲氧基硅烷（MPS）和醋酸钙进行改性，展示了基于PMMA的生物活性骨水泥的潜力。在本研究中，在模拟体液（Kokubo溶液）中研究了PMMA粉末种类对凝固时间、磷灰石形成和抗压强度的影响。当PMMA粉末的平均分子量为100,000或更低时，用在220℃煅烧的醋酸钙改性的骨水泥可在15分钟内凝固。在PMMA粉末中添加在120℃煅烧的醋酸钙需要更长的凝固时间。对于起始于分子量为100,000或更低的PMMA粉末的骨水泥，改性骨水泥在Kokubo溶液中浸泡1天内形成了磷灰石层。对于起始于分子量为100,000和56,000的骨水泥，改性骨水泥的抗压强度超过70MPa。在Kokubo溶液中浸泡7天后，由分子量为100,000的PMMA粉末组成的改性骨水泥的抗压强度下降幅度小于由分子量为56,000的PMMA粉末组成的改性骨水泥。这些结果表明，当使用具有合适分子量的PMMA粉末时，可以生产出具有适当凝固时间和机械强度的生物活性PMMA骨水泥。这种类型的生物活性PMMA骨水泥设计导致了用于骨替代物的生物活性材料的新发展。
