Abstract
Tetracalcium phosphate (TTCP) is one of the most common starting materials of calcium phosphate-based ceramic bone cement. However, the ceramic bone cement has a critical drawback such as poor mechanical properties and slow setting time. In this study, the thermodynamically unstable tricalcium silicate ($C_3S$) was synthesized and introduced into TTCP-based bone cement to enhance the mechanical and setting properties of the bone cement. The cement properties and compressive strength of hardened TTCP-cement with the addition of $C_3S$ were examined in terms of the contents of $C_3S$ and hardener. First, TTCP and DCPD with $C_3S$ (0; 5; 10 wt%) were ball milled for 24 hrs and then dried at $60^{\circ}C$ for 1 day. The sample powder was mixed with the solution of a hardener ($Na_2HPO_4{\cdot}nH_2O$) with various concentrations (0, 0.5, 1.0 mol/L). The hydration of TTCP and DCPD resulted in the precipitation of HA crystallites and is the major driving force of setting for the TTCP-based bone cements. The XRD peaks of the hardened cements were identified as a mainly HA. With the addition of $C_3S$, the cement showed a longer setting reaction time and lower setting temperature. However, the addition of hardener caused a higher setting temperature and faster setting time. The Vicat setting time decreased with the addition of hardener, but showed anomalous results with the $C_3S$ content. The incorporation of both hardener and $C_3S$ to cements would come with both the increase of mechanical strength and the reduction of setting time. However, the effect of $C_3S$ addition was not significant.