Skin hypersensitivity was investigated in guinea-pig maximization tests with extracts from pellets of conventional polymethyl-methacrylate (PMMA) bone cements (Palacos R, Simplex RO) and a new methylmethacrylate/n-decylmethacrylate/isobornylmethacrylate (MMA/DMA/IBMA) mixture (Boneloc), but none of the three cements produced evidence of delayed contact hypersensitivity. Testings of the pure monomer compounds showed MMA to be an extreme sensitizer, whereas DMA and IBMA were only mild sensitizers. Fingers from three brands of surgical rubber gloves and a polystyrene-butadiene glove were immersed in water and filled with conventional MMA monomer, MMA/DMA/IBMA monomer or bone cements in the dough state, allowing cure inside the glove. In the surrounding water, no DMA or IBMA could be detected. The MMA concentrations were lower with MMA/DMA/IBMA monomer and curing Boneloc cement. The most resistant to conventional PMMA cement was one of the rubber gloves, whereas the polystyrene-butadiene glove allowed the highest penetration, and even dissolved in MMA monomer. The potential occupational hazard of skin sensitization is reduced with MMA/DMA/IBMA bone cement, preferably in combination with rubber gloves; but also polystyrene-butadiene gloves provide adequate protection.

A new formulation of acrylic bone cement [methylmethacrylateln-decylmethacrylate/ isobornylmethacrylate (MMA/DMA/IBMA)] developed with the purpose of reducing the biologic adverse effects of bone cements was analyzed by high performance liquid chromatography for residual content of monomers and aromatic amines from the accelerator system [dimethyl-p-toluidine (DMPT), dihydroxypropyl-p-toluidine (DHPPT)] in the cured cement and for concentrations of these constituents in hydrophilic and lipophilic eluates. In comparison with conventional polymethyl-methacrylate acrylics a considerable reduction of both released and residual MMA was experienced, being about 10-to 15-fold. The residual content of the new DMA and IBMA monomers were 0.35% and 0.66%, respectively, in cured cement after 72 h and these could only be detected in the paraffin eluates. The residual content of aromatic amines was considerably reduced with the new cement formulation. No DMPT could be detected and the DHPPT represented a 3-to 4-fold reduction in cured cement and a 8-to 10-fold reduction in eluates. The residual DHPPT content of about 0.07% was found to be practically constant with time. It is concluded that MMA/ DMA/IBMA cement cures faster and more completely.

The genotoxicity of conventional polymethylmethacrylate (PMMA) and a new formulation of bone cement: methylmethacrylate/n-decylmethacrylate/isobornylmethacrylate (MMA/DMA/IBMA) were tested by micronucleus test and reverse mutation assays of Salmonella typhimurium (Ames test). In extracts from cement pellets (37 degrees, 72 hr) with water and water/ethanol the concentration of MMA was reduced by 13-19 times with the new formulation and the concentrations of accelerators were reduced by 4-5 times. New chemical constituents (DMA, IBMA, dihydroxy-propyl-p-toluidine) were found in negligible concentrations. In the micronucleus test all three cement brands were found non-mutagenic and in the Ames test scattered increased revertant ratios were found without differences between the three brands. The new formulation does not possess any increased risk of genotoxicity.