Effects of poloxamer additives on strength, injectability, and shape stability of beta-tricalcium phosphate cement modified using ball-milling.

A new CPC was developed in this study using a β-TCP powder mechano-chemically modified by ball-milling. The prototype CPC exhibits excellent fluidity for easy injection into bone defects; however, there is a risk of leakage from the defects immediately after implantation due to its high fluidity. The addition of poloxamer, an inverse thermoresponsive gelling agent, into CPC optimizes the fluidity. At lower temperatures, it forms a sol and maintains good injectability, whereas at the human body temperature, it transforms to a gel, reducing the fluidity and risk of leakage. In this study, the effects of poloxamer addition of 3, 5, and 10 mass% on the injectability, shape stability, and strength of the prototype CPC were evaluated. The calculated injectability of the prototype CPC pastes containing three different poloxamer contents was higher than that of the CPC paste without poloxamer for 15 min at 37 °C. Furthermore, the shape stability immediately after injection of the three CPC pastes with poloxamer was higher than that of the CPC paste without poloxamer. After 1 week of storage at 37 °C, the compressive strength and diametral tensile strength of the CPC compacts containing 10 mass% poloxamer were similar to those of the CPC compact without poloxamer. Additionally, the CPC compacts containing 10 mass% poloxamer exhibited clear plastic deformation after fracture. These results indicate that the addition of poloxamer to the prototype CPC could reduce the risk of leakage from bone defects and improve the fracture toughness with maintaining the injectability and strength.