Bioactive polymethyl methacrylate-based bone cement: Comparison of glass beads, apatite- and wollastonite-containing glass-ceramic, and hydroxyapatite fillers on mechanical and biological properties

A new bioactive bone cement (designated GBC) consisting of polymethyl metha crylate (PMMA) as an organic matrix and bioactive glass beads as an inorgan ic filler has been developed. The bioactive beads, consisting of MgO-CaO-Si O2-P2O5-CaF2 glass, have been newly designed, and a novel PMMA powder was s elected. The purpose of the present study was to compare this new bone ceme nt GBC's mechanical properties in vitro and its osteoconductivity in vivo w ith cements consisting of the same matrix as GBC and either apatite- and wo llastonite-containing glass-ceramic (AW-GC) powder (designated AWC) or sint ered hydroxyapatite (HA) powder (HAC). Each filler added to the cements amo unted to 70 wt %. The bending strength of GBC was significantly higher than that of AWC and HAC (p < 0.0001). Cements were packed into intramedullar c anals of rat tibiae in order to evaluate osteoconductivity as determined by an affinity index. Rats were sacrificed at 2, 4, and 8 weeks after operati on. An affinity index, which equaled the length of bone in direct contact w ith the cement expressed as a percentage of the total length of the cement surface, was calculated for each cement. At each time interval studied, GBC showed a significantly higher affinity index than AWC or HAC up to 8 weeks after implantation (p < 0.03). The value for GBC increased significantly w ith time up to 8 weeks (p < 0.006). The handling property of GBC was compar able with that of PMMA bone cement. Our study revealed that the higher oste oconductivity of GBC was due to the higher bioactivity of the bioactive gla ss beads at the cement surface and the lower solubility of the new PMMA pow der to MMA monomer. In addition, it was found that the smaller spherical sh ape and glassy phase of the glass beads gave GBC strong enough mechanical p roperties to be useful under weight-bearing conditions. GBC shows promise a s an alternative with improved properties to the conventionally used PMMA b one cement. (C) 2000 John Wiley & Sons, Inc. J Biomed Mater Res, 51, 258-27 2, 2000.