Mechanical Properties and Histological Evaluation of Bone Grafting Materials Containing Different Ratios of Calcium Phosphate Cement and Porous β-tricalcium Phosphate Granules

[Objective] : Although calcium phosphate cement (CPC) is a bone substitute material having good formativeness, biocompatibility, and osteoconductivity, it has very slow biodegradability in vivo. This study aimed to create a new porous bone cement with enough strength, good formativeness, biodegradation, and osteoconductivity for bone regeneration by adding porous β-tricalcium phosphate (β-TCP) granules to CPC. [Methods] : A commercially available CPC and porous β-TCP were used in this study. Three testing materials with different mixing ratios of CPC and β-TCP (C0, C30 and C50, having mixing ratios of β-TCP of 0, 30, and 50 wt%, respectively) were examined. We evaluated the basic materialological properties in vitro. In addition, biodegradation and osteoconductivity were evaluated in vivo by implantation in rabbit femurs. [Results] : The setting times for C30 (15 minutes) and C50 (18 minutes) were thought to be within a clinically acceptable range. Although the compressive strength decreased with increasing content of β-TCP, that of C50 was the same as for cancellous bone. The porosity and permeability increased with addition of more β-TCP granules. Histological evaluation revealed that biodegradability of the material increased with the addition of more β-TCP granules and the material had good bioactivity. Notably, at 36 weeks after implantation, C50 was almost completely resorbed and replaced by regenerated bone. [Conclusions] : The results of this study suggested that the composite created by adding equal weight percent of porous β-TCP granules to CPC paste had good biodegradability and adequate mechanical strength, and was adaptable as a bone substitute for bone defect repairs.