Bone cements based on ground β-tricalcium phosphate with sufficient compressive strengths and short hardening time

In this study, we investigated the hardening processes and compressive strengths of binary and ternary calcium phosphate cements based on β-tricalcium phosphate [Ca3(PO4)2] (β-TCP) ground by a mortar grinder. The cements were prepared by adding tetracalcium phosphate [Ca4(PO4)2O] (TTCP) and/or calcium hydrogenphosphate dihydrate [CaHPO4·2H2O] (DCPD) to the ground β-TCP, which hardened on mixing with disodium hydrogenphosphate [Na2HPO4] aqueous solution. The binary cement β-TCP/TTCP with a molar ratio of 2:1 showed a compressive strength of 35 MPa after hardening, which is based on a 1-day acid–base reaction. The ternary cement β-TCP/TTCP/DCPD with molar ratios of β-TCP (50–60%), TTCP (20–30%), and DCPD (14–20%,) showed early hardening and an adequate compressive strength of 30–43 MPa after a 1-day reaction. In particular, the ternary cement with a molar ratio of 3:2:1 (β-TCP:TTCP:DCPD) showed compressive strengths of 17, 43, and 56 MPa after 1 h in air, and 1 and 7 days’ soaking in saline solution, respectively. These ternary cements hardened to give well-connected acicular apatite crystals. The hardening process involved hydrolysis of the ground β-TCP and acid–base reactions of β-TCP/TTCP and DCPD/TTCP.