Effects of high-energy ball-milling on injectability and strength of β-tricalcium-phosphate cement

• β-TCP powder was mechano-chemically modified using ZrO2 ball-milling for 24 h.
• Cement paste using modified β-TCP successfully exhibited sufficient injectability.
• Modified cement compact exhibited an appropriate setting time.
• Modified cement compact exhibited a drastic improvement in compressive strength.

Calcium phosphate cement (CPC) offers many advantages as a bone-substitution material. The objective of this study is to develop a new CPC that simultaneously exhibits fine injectability, a short setting time, and high strength. β-tricalcium phosphate (β-TCP, control) powder was ball-milled for 24 h to produce a new cement powder. The modified β-TCP after 24 h milling (mβ-TCP-24 h) exhibited excellent injectability even 1 h after mixing. The mechanical properties of the set cement (compact) were evaluated using compressive strength (CS) and diametral tensile strength (DTS) testing. The CS and DTS values of the mβ-TCP-24 h compacts were 8.02 MPa and 2.62 MPa, respectively, at 5 h after mixing, and were 49.6 MPa and 7.9 MPa, respectively, at 2 weeks after mixing. All the CS and DTS values of the mβ-TCP-24 h compacts were significantly higher than those of the control for the same duration after mixing. These results suggest that the mechano-chemically modified β-TCP powder dissolves rapidly and accelerates hydroxyapatite precipitation, which successfully shortens the cement setting time and enhances the strength. This study supports that mβ-TCP-24 h is a promising candidate for use in injectable CPCs with improved strength.