Influence of the modification of P/L ratio on a new formulation of acrylicbone cement

The use of smaller powder/liquid (P/L) ratio favours the handling and wetti ng of poly(methyl methacrylate) (PMMA) beads in bone cement formulations. I n this paper a P/L ratio of 1.86 is tested to overcome adhesion problems fo und in hydroxypropyl methacrylate (HPMA) modified bone cements and the infl uence on bone cement characteristics was analysed. The reduction of the P/L ratio leads to higher temperature peaks and shorter setting times, whereas the residual monomer content increases slightly. Water uptake obeys the di ffusion laws, and the introduction of a more hydrophilic monomer gives rise to an increase of this parameter, which does not present significant chang es with modification of the P/L ratio. Polymerization shrinkage is slightly greater because of the introduction of higher proportions of monomer in th e formulation. Mechanical properties are similar to those obtained with con ventional P/L ratios. The analysis of scanning electron microscopy (SEM) re veals an improvement of the adhesion between phases with respect to P/L = 2 formulations. (C) 1999 Elsevier Science Ltd. All rights reserved.