Calcium Phosphate Cement Modified with Silicon Nitride/Tricalcium Phosphate Microgranules

Tetracalcium phosphate/monetite biocement was modified with 10 and 30 wt. % addition of highly porous silicon nitride/α-tricalcium phosphate (αTCP) microgranules with various content of αTCP. A composite cement powder mixture was prepared using mechanical homogenization of basic components. The accelerated release of dexamethasone from composite cement was revealed, which indicates their possible utilization for controlled drug release. The wet compressive strength of cements (<17 MPa) was significantly reduced (more than 30%) in comparison with the unmodified cement and both compressive strength and setting time were influenced by the content of αTCP in microgranules. The addition of microgranules caused a 20% decrease in final cement density. Microgranules with a higher fraction of αTCP showed good in vitro SBF bioactivity with precipitation of hydroxyapatite particles. Microstructure analysis of fractured cements demonstrated excellent interconnection between microgranules and cement calcium phosphate matrix, but also showed lower mechanical strength of microgranule cores.