Injectable Calcium Sulfate-Calcium Phosphate Composite as a Bone Substitute – Material Properties And Histological Analysis

Various synthetic materials as bone substitute have been tested with unreliable clinical application. Calcium sulfate has been used as a bone-graft substitute. Calcium phosphate is regarded to have a longer resorption period for further scaffold support. An injectable form of a calcium sulfate-calcium phosphate composite was created to be a bone substitute. This study is to evaluate the mechanical properties and histological changes in a rabbit model. The mean compression strength was 22.17 ± 1.37 Mpa. The mean bending strength was 11.19 ± 0.72 Mpa. The average setting time was 12.5 ± 0.5 min. The histological studies showed that osteoclasts could be identified with active mineral resorption associated with new-bone formation at 4 weeks. Osteoblasts could also be found adjacent to the osteoclasts indicating initiation of bone ingrowth. Extensive cellular activity at the interface between peripheral bone and the calcium sulfate-calcium phosphate bone substitute suggested active bone-ingrowth at 8 weeks. At 12 weeks, the bone defect was filled with trabecular bone. Extensive trabecular bone formation appeared in the original bone defect region. There was no fibrous tissue between the material and the bone. The injectable property of this composite made it possible to fill gaps easily and efficiently and avoid fibrous tissue ingrowth during the bone healing process. The composite provides instant mechanical support of the recipient site, which avoided early mechanical failure.