Evaluation of Biphasic Calcium Phosphate Cement in Rat Calvarial Model

Abstract

Biphasic calcium phosphate (BCP) cement, consisting of an α-tricalcium phosphate-tetracalcium phosphate as the only solid phase and a calcium phosphate solution (Ca-P soln) as the liquid phase, was recently reported. The BCP cement provided sufficient handling and physical properties for clinical uses. Objective of this study was to evaluate the BCP cement when used for repairing artificially created bone defects in rat calvaria. The sample of BCP cement was prepared by mixing BCP powder with Ca-P soln at P/L of 3.0. A commercially available calcium phosphate cement, Biopex-R, was used as a positive control. Surgically created bone defects were filled with the BCP cement or the control cement. A defect with no filling material was used as a negative control. At 0 and 8 weeks after surgery, X-ray micro-CT image 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. After microscopic examination, computer-assisted histometric measurements of newly formed bone (NB) were performed using NIH image analysis. Defect closure (DC) was determined by measuring the distance between defect margin and new bone margin, and was expressed as a percentage of total defect width. The BCP cement kept original graft shape, and defects filled with the cement were mostly closed by NB. The control cement inadequately maintained original graft shape, and defects filled with the control cement were partially closed by NB. The negative control showed almost no bone formation in the defects. The DC rate of the BCP cement exhibited apparently larger than that of the control cement (p<0.05). These results were also confirmed by fluorescent labelling analysis and X-ray micro-CT observations. The results indicated that the BCP cement had osteoconductive potential for bone defects.