The Assay of Bone Reaction after Implantation of Calcium Sulfate and A Composite of Calcium Sulfate and Calcium Phosphate
The in vivo implantation of calcium sulfate and a composite of calcium sulfate and calcium phosphate of the proximal epiphysis of tibia of the rabbit was investigated to evaluate biocompatibility, bioabsorbability and biodegradability. The materials were in situ for 6, 12 and 24 weeks in 3 different groups of rabbits in all 6 cases. Light microscopy reveals calcium sulfate in bone marrow is completely resorbed and replaced by connective tissue and fatty tissue. Significant osteogenesis is noted once calcium sulfate contacts with periosteum and endosteum. We do not recommend use of calcium sulfate as filler of bone defect because new bone formation is not ideal due to fast absorption of implant. A composite of calcium sulfate and calcium phosphate is slowly resorbed. The absorbed calcium sulfate will be used as materials of bone matrix. It will cause a porous effect in composite. The newly formed bone integrates into the implant along with the pore and contacts directly with crystals of calcium phosphate. Osteoblasts are in direct contact with implanted granules of calcium phosphate. There is no evidence of acute or chronic inflammation. Therefore a composite of calcium sulfate and calcium phosphate is considered a good choice of bone defect filler.