Fundamental Study of Bioactivity of Inorganic Materials

有几种无机材料能自发地与活骨结合。它们被称为生物活性材料，并已在临床上用作一些骨替代品。然而，它们的骨结合机制尚未完全了解。在本研究中，控制生物活性的因素进行了研究。通过体外和体内实验证实，Ceravital^<<0！>>-型含磷灰石微晶玻璃与生物玻璃和微晶玻璃A-W相似，也是通过在其表面形成一层富含Ca、P的层与活骨结合。X射线衍射分析表明，A-W微晶玻璃与羊骨界面处形成的富Ca、P层确为体外实验所预期的磷灰石层。对微晶玻璃A-W在模拟体液中的表面反应分析表明，微晶玻璃表面的磷灰石层是由溶出的Ca（II）和Si（IV）离子与体液中的P（V）离子反应诱导磷灰石成核而形成的，以及通过消耗来自流体的Ca（II）和P（V）离子来实现磷灰石的生长。CaO-SiO_2-P_2O_5和CaO-SiO_2-Al_2O_3玻璃在模拟体液中的表面反应分析表明，玻璃表面磷灰石的形成仅限于CaO、SiO_2基组成区，这是因为玻璃中溶解的Ca（II）和Si（IV）离子在表面磷灰石的形成中起着协同作用。Ca（II）离子增加了周围流体相对于磷灰石的过饱和度，而Si（IV）离子诱导磷灰石成核。

A few kind of inorganic materials spontaneously bond to living bone. They are called bioactive materials and already clinically used as some bone substitutes. Their bone-bonding mechanism is not, however, fully understood. In the present study, factors governing the bioactivity was studied. It was confirmed by in vitro as well as in vivo experiments that Ceravital^<<0!>>-type apatite-containing glass-ceramic also bond to living bone through a Ca, P-rich layer which is formed on its surface in the body, similar to Bioglass and glass-ceramic A-W. It was shown by X-ray microdiffraction that the Ca, P-rich layer formed at the interface between glass-ceramic A-W and the bone of a sheep is indeed an apatite layer as expected from in vitro experiments. Analysis of surface reaction of glass-ceramic A-W in a simulated body fluid showed that the apatite layer on the surface of the glass-ceramic is formed by a nucleation of the apatite which is induced by the reaction of Ca (II) and Si (IV) ions dissolved from the glass-ceramics with P (V) ion in the fluid, and growth of the apatite which is achieved by consuming Ca (II) and P (V) ions from the fluid. Analysis of surface reaction of CaO-SiO_2-P_2O_5 and CaO-SiO_2-Al_2O_3 glasses in a simulated body fluid showed that apatite formation on the surfaces of glasses is restricted to CaO, SiO_2-based compositional region, because the Ca (II) and Si (IV) ions dissolved from glasses play cooperative important role in forming the surface apatite. The Ca (II) ion increases the degree of the supersaturation of the surrounding fluid with respect to the apatite, whereas the Si (IV) ion induces apatite nucleation.