Bioactive bone cement: Effect of filler size on mechanical properties and osteoconductivity

A bioactive bone cement (designated GBC), consisting of bioactive glass bea ds as an inorganic filler and poly(methyl methacrylate) (PMMA) as an organi c matrix, has been developed. The purpose of the present study was to exami ne the effect of the size of the glass beads added as a filler to GBC on it s mechanical properties and osteoconductivity. Serial changes in GBC with t ime were also examined. Four different sizes of beads (mean diameters 4, 5, 9, and 13 mum) consisting of MgO-CaO-SiO2-P2O5-CaF2 glass were added to fo ur GBC mixes in a proportion df 70 wt %. The bending strength of GBC increa sed as the mean size of the glass beads decreased. The four GBC mixes were packed into the intramedullary canals of rat tibiae to evaluate osteoconduc tivity, as determined by an affinity index. Rats were sacrificed at 4 and 8 weeks after surgery. The affinity index, which equaled the length of bone in direct contact with the cement surface expressed as a percentage of the total length of the cement surface, was calculated for each cement at each interval. Histologically, new bone had formed along the surface of all type s of GBC within 4 weeks. At each time interval, there was a trend for the a ffinity index of GBC to increase as the mean glass bead size decreased. The affinity indices for all types of GBC increased significantly with time up to 8 weeks. The handling properties of GBC were comparable to those of con ventional PMMA bone cement. We concluded that, considering both mechanical properties and osteoconductivity, GBC made with smaller sized glass beads a s filler was the most suitable cement. GBC shows promise as an alternative bone cement with improved properties compared to conventional PMMA bone cem ent. (C) 2001 John Wiley & Sons, Inc.