Development of bioactive PMMA-based cement by modification with alkoxysilane and calcium salt

Poly (methyl methacylate) (PMMA) bone cement is one of the popular bone-rep airing materials for fixation of artificial hip joints. Significant problem s on the PMMA bone cement are caused by loosening at the interface between bone and the cement, since the cement does not show bone-bonding, i.e. bioa ctivity. Development of PMMA bone cement capable of bone-bonding has been t herefore long desired. The prerequisite for an artificial material to show bone-bonding is the formation of a biologically active bone-like apatite la yer on its surface when implanted in the body. The same type of apatite for mation can be observed on bioactive materials even in a simulated body flui d (Kokubo solution) with ion concentrations nearly equal to those of human blood plasma. Fundamental researches for bioactive glasses and glass-cerami cs revealed that the apatite deposition is initiated by release of Ca2+ ion s from the material into the body fluid, and by catalytic effect of Si-OH g roups formed on the surface of the material. These findings lead an idea th at novel bioactive cement can be designed by incorporation of Si-OH groups and Ca2+ ion into PMMA bone cement. In the present study, PMMA bone cement is modified with 20 mass % of various kinds of alkoxysilanes and calcium sa lts, and its apatite-forming ability was evaluated in Kokubo solution. The apatite formation was observed on the surface of the modified cements conta ining 20 mass % of CaCl2, irrespective of the kind of the examined alkoxysi lane. On the other hand, the apatite formation was observed on the cement c ontaining CaCl2, Ca(CH3COO)(2) or Ca(OH)(2), but not on the cement containi ng CaCO3 or beta -Ca-3(PO4)(2), even when the cement contains 3-methacrylox ypropyltrimethoxysilane (MPS). The results indicate that modification with alkoxysilane and calcium salts showing high water-solubility is effective f or providing PMMA bone cement with bioactivity. (C) 2001 Kluwer Academic Pu blishers.