PMMA-based composite materials with reactive ceramic fillers: IV. Radiopacifying particles embedded in PMMA beads for acrylic bone cements

New acrylic bone cements were prepared from alumina particles previously tr eated by 3-(trimethoxysilyl)propylmethacrylate (gamma -MPS) and embedded in poly(methylmethacrylate-co-ethylacrylate) beads with about 7 mol% of ethyl acrylate repeating units, The encapsulation was performed through a conven tional suspension polymerization process, The influence of (i) the concentr ation of the dispersion stabilizer and (ii) the alumina content upon the sh ape, size, and size distribution of the acrylic beads was studied. Cements were prepared from each batch by hand-mixing alumina-filled acrylic beads w ith a liquid monomer mixture containing methyl methacrylate, n-butyl methac rylate, and N,N-dimethyl-p-toluidine. Benzoyl peroxide was previously added to the solid part. The powder-to-liquid ratio was equal to 2 for each form ulation, Compressive strength of cured cement decreases with alumina conten t, whereas compressive modulus remains roughly constant. These results are in contradiction to those obtained for cements based on a mixture of gamma -MPS-treated alumina and unfilled acrylic beads. Nevertheless, they are int erpreted in terms of alumina arrangement in the cement. In the first case, alumina particles contribute to the reinforcement of the dispersed acrylic phase, with poor benefits for the whole materials. In the second ease, they allow the reinforcement of the continuous acrylic phase and, therefore, th e cement's one, (C) 2000 John Wiley & Sons, Inc.