Abstract
The purpose of this study was to elucidate the effect of amount of ceramic cement powder on drug release from bioactive bone cement. The associated bone‐bonding strength was also investigated. The bioactive bone cement under investigation consisted of bisphenol‐α‐glycidyl methacrylate (Bis‐GMA), triethylene‐glycol dimethacrylate (TEGDMA) resin and a combination of apatite‐ and wollastonite‐containing glass‐ceramic (A‐W GC) powder. A‐W GC powder (50%, 70% and 80% w/w) containing 5% cephalexin (CEX) powder hardened within 5 min after mixing with Bis‐GMA/TEGDMA resin. The compressive strength of the cement with or without drug increased with increasing the amount of ceramic powder. The compressive strength of the 80% ceramic cement without the incorporation of cephalexin was 194 MPa. This compressive strength was about 3 times higher than that for polymethylmethacrylate cement. After the cement was implanted in the proximal metaphysis of the tibiae of male rabbits, the failure load for the cement was found to increase with increasing of the amount of ceramic powder. This finding suggested that the cement formed a bonding with bone. In vitro CEX release from bioactive bone cement pellets in a simulated body fluid at pH 7.25 and 37○C continued for more than 2 weeks. Drug release profile followed the Higuchi equation initially, but not at later stages. The drug release rate increased with increasing amount of ceramic powder in the mixture. Since the pore volume of the cement increased with increasing of amount of ceramic powder, the drug diffused in the pores between the ceramics particle and polymer matrix. As hydroxyapatite precipitated on the cement surface, the drug release rate decreased, as observed at the later release stage. These results suggest that varying the amount of ceramic powder in the cement system could control the drug release rate from bioactive bone cement.