Development of new bone cement utilizing low toxicity monomers.

Acrylic bone cement is self-curing cement comprising of liquid and powder component of methyl methacrylate (MMA). It has been used extensively in orthopedics; however, adverse effects were associated with its use. Hence we investigated in this paper the possibility of new cement utilizing methacrylates with lower toxicity than MMA. LD50s of candidate monomers were determined with administration to the medullary cavity of the rat's femur. 2-Ethylhexyl methacrylate (EHMA) and trimethylolpropane trimethacrylate (TMP) demonstrated greater LD50 values of 187 mg/kg and 380 mg/kg, respectively, than MMA (108 mg/kg); they were selected as the liquid components of the new cement. The copolymer of EHMA and cyclohexyl methacrylate was then selected as the powder component. With this combination, we developed the new cement (EHMA cement).Temperature rise during polymerization of EHMA cement was 9 degrees C-13 degrees C, which was significantly lower than that of conventional cement. The compression strength of the polymerized EHMA cement was 57 MPa without TMP, and 67 MPa with TMP (15 wt%). Thus we concluded that new EHMA cement was slightly inferior in the compression strength than the conventional cement. However, it was characterized by the low toxicity of utilized monomers and the low temperature rise during polymerization.