Osteoconductivity of Biphasic Calcium Phosphate Cement in Rat Calvarial Model

Objectives: A calcium phosphate cement consisting of an α-tricalcium phosphate-tetracalcium phosphate biphasic calcium phosphate (BCP) as the only solid phase and calcium phosphate solution as the liquid phase was developed. BCP cement provided good handling properties, desired hardening time, sufficiently high strengths, and was expected to have good biocompatibility and osteoconductivity. The aim of this study was to evaluate BCP cement when used for repairing artificially created calvarial bone defects (diameter: 5mm) of rats.
Methods: BCP cement included trisodium citrate anhydrous and polyvinylpyrrolidone-k25 as water reducing agent and washout resistance enhancer, respectively. Cement powder and liquid were mixed at powder/liquid ratio of 3. A commercially available calcium phosphate cement, Biopex-R, was used as a positive control. Defects filled without material were used as the negative control. Surgically created bone defects were filled with BCP cement or a control cement. At 0 and 8 weeks after surgery, x-ray micro-CT for each surgical site was taken. At 8 weeks after the surgery, the animals were sacrificed, and biopsies were obtained. Subsequently, the sections were subjected to HE and TRAP staining and examined under a microscope. The value of new bone formation in each surgical site was evaluated quantitatively using NIH image analysis. Student’s t-test was used to establish statistical significance.
Results: The BCP cement paste kept the original graft shape and exhibited excellent washout resistance. The defects were almost completely closed by newly formed bone. The control cement kept original graft shape inadequately, and the defects were partially closed by newly formed bone. BCP cement consistently showed faster (p<0.05) bone replacement when compared to the control cement. The defects without material, showed almost no bone formation in the defects. These results were also confirmed by x-ray micro-CT observations.
Conclusions: The results indicated that the BCP-based cement has high expected efficacy for repairing bone defects.