Effects of tricalcium silicate addition on basic properties of crtricalcium phosphate cement

Addition of tricalcium silicate (Ca₃SiO₅; alite) to apatite cement (AC) may be effective to increase the osteoconductivity of AC. However, only limited studies have been made so far for the effect of alite addition on the basic setting properties of α-tricalcium phosphate [α-Ca₃ (PO₄)₂; α-TCP] based cement. In the present study, effects of added alite on the basic properties of α-TCP based AC was studied. α-TCP powder containing 0.0, 2.5, 5.0, 10.0, and 20.0 mass% alite were mixed with 0.25 mol/L sodium dihydrogen phosphate solution (NaH₂PO₄) and the obtained cement pastes were stored in 100% relative humidity at 37°C. Initial setting time was delayed with increase in alite content. The 2.5-5.0 mass% of alite added cements were completely transformed into apatite within 24 h and the final mechanical strength of the set cement increased reaching approximately 15 MPa in terms of diametral tensile strength when compared with alite-free cement which showed approximately 9 MPa. However, 10.0-20.0 mass% of alite addition suppressed the apatite formation and decreased the mechanical strength of the set cement. We concluded therefore, that addition of appropriate amount of alite to α-TCP is desirable with respect to the setting properties of AC.