Bioactive bone cement: Effect of silane treatment on mechanical propertiesand osteoconductivity

A novel bioactive bone cement (GBC) was developed with newly designed bioac tive MgO-CaO-SiO2-P2O5-CaF2 glass beads as the inorganic filler and high mo lecular weight poly(methyl methacrylate) as the organic matrix. The purpose of this study was to examine the relationship between the amount of the si lane coupling agent (gamma -methacryloxy propyl trimethoxy silane) used to treat the glass beads and the mechanical and biological properties of the r esultant bone cement. Serial changes in the cement over time were also inve stigated. Five different kinds of cement, in which the glass beads were tre ated with different amounts of the coupling agent, were prepared. The quant ities of the coupling agent were 0 (control), 0.1, 0.2, 0.5, and 1.0% (w/w) of the glass beads, and the cements were designated GBCs0, GBCs0.1, GBCs0. 2, GBCs0.5, and GBCs1.0, respectively. After soaking in water at 75 degrees C for 5 days, GBCs0.1 and GBCs0.2 had significantly higher bending strength s than the other cements. Each GBC was packed into intramedullar canals of rat tibiae to evaluate osteoconductivity, as determined by affinity indices . Rats were killed 4 and 8 weeks after the operation. The affinity index wa s calculated for each GBC and equaled the length of bone in direct contact with the cement and was expressed as a percentage of the total length of th e cement surface. Histologically, new bone had formed along all of the GBC surfaces within 4 weeks. At each time interval, a decreasing trend in the a ffinity index of GBC was found as the amount of the coupling agent increase d. At 8 weeks, no significant change in the affinity index occurred when th e amount of the coupling agent increased from 0 to 0.2%, whereas a signific ant decrease in the affinity index was observed when the amount of the coup ling agent increased from 0 to 0.5 or 1.0%. The affinity indices for all th e GBCs increased significantly up to 8 weeks. When both the mechanical prop erties and osteoconductivity were taken into consideration, GBCs0.1 and GBC s0.2 were the best cements, and they showed excellent osteoconductivity and strong enough mechanical properties for clinical use. (C) 2001 John Wiley & Sons, Inc.