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

Abstract

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.