Hydroxyapatite/PMMA composites as bone cements

Currently PMMA is the polymer most commonly used as a bone cement for the fixation of total hip prostheses. Ideally, a bone cement material should be easy to handle, biologically compatible, nonsupporting of oral microbial growth, available in the particulate and molded forms, easy to obtain, nonallergenic, adaptable to a broad range of dental and medical applications, in possession of high compressive strength, and effective in guided tissue regenerative procedures. One of the problems associated with the conventional types of bone cement used is their unsatisfactory mechanical and exothermic reaction properties. The purpose of this in vitro study was to investigate and compare the mechanical properties (three-point bending strength, energy-to-break, and modulus of elasticity) and physical properties (setting time, water sorption, and exothermic heat) of HA/PMMA (HA group) and bovine-bone originated HA/PMMA (BB group) composites. Composites samples were fabricated by admixing method. It was found that the addition of HA and BB particles increased the water sorption. Generally 10 v/o 20 v/o HA and 0 v/o to 10 v/o BB ratio combinations had significant beneficial effects on the mechanical properties. The heat generated during polymerization was influenced by the different admixtures. More than 40 v/o HA and 40 v/o BB should be mixed into PMMA to reduce the peak temperature. Overall evaluation indicated that the BB group had better properties than the HA group.