Setting properties of bone cement with added synthetic hydroxyapatite.

Synthetic hydroxyapatite powder was added to commercial bone cement to improve its physico-mechanical properties. The study of the setting properties showed the considerable effect of hydroxyapatite (HA) on the polymerization process; in particular statistical treatment of the experimental results revealed a significant relative minimum of the exothermic peak value at HA 5% weight percentage--an effect attributed to the HA 'crumbling' action on the microporosity features. The relationship between the interface (air and monomer bubbles/acrylic resin) versus dough composition was evaluated: the comparison between this last one and the corresponding internal energy variation supports the above hypothesis.