BIOACTIVE BONE-CEMENT - EFFECT OF THE AMOUNT OF GLASS-CERAMIC POWDER ON BONE-BONDING STRENGTH

We examined the influence of the proportion of glass-ceramic powder in a bioactive bone cement of our formula on the bone-bonding ability of cement. Changes in cement bonding with time also were examined. The b ioactive bone cement consisted of MgO-CaO-SiO2-P2O5-CaF2 glass-ceramic powder (AW-GC powder) and bisphenol-alpha-glycidyl methacrylate (Bis- GMA)-based resin. AW-GC powder was added to the cement as 0%, 30%, 50% , 70%, and 80% w/w. Rectangular plates (2 x 10 x 15 mm) of each cement with polished surfaces were implanted into the proximal metaphysis of the tibiae of male rabbits, and the failure load was measured by deta ching tests 10 and 25 weeks after implantation. The failure loads of e ach cement were 0% = 0.03, 30% = 1.52, 50% = 2.67, 70% = 3.56, and 80% = 5.59 kg at 10 weeks, and 0% = 0.05, 30% = 1.68, 50% = 2.77; 70% = 3 .80, and 80% = 6.37 kg at 25 weeks. Observation of the cement-bone int erface revealed that all bioactive bone cements (30%-80%) formed direc t contact with bone whereas intervening fibrous tissue was observed in all specimens of the 0% group. By scanning electron microscopy, all b ioactive bone cements (30%-80% groups) showed direct contact with bone at the cement-bone interface. In the 0% group, direct contact with bo ne at the cement-bone interface was not observed. By electron-probe mi croanalysis, a Ca-P-rich layer was not detected at the cement-bone int erfaces of the 30%-70% bioactive bone cements, but in some samples of the 80% cement specimens a thin Ca-P-rich layer (3 mu m thick) was obs erved at the interface at 10 and 25 weeks after implantation. These re sults show that all of the bioactive bone cements tested had the abili ty to bond to bone and to function as bioactive composites of ceramics and polymers. (C) 1998 John Wiley & Sons, Inc.