Study On The α-tricalcium Phosphate Bioactive Bone Cements

Calcium Phosphate is an important inorganic component of animal skeleton. Compared with other bone repair materials, calcium phosphate cement (CPC) has good biocompatibility, biodegradability, remodellability and self-solidifiability in body. So CPC was a standard material in repairing of bone defects. In recent years, the research of composite biomaterials based CPC went on broadly, because CPC possesses advantage of convenient moulding in clinic operation and good anastomose with self-boons. In this study, the preparation of a new-styleα-TCP CPC, its formula, bioactivity in simulated body fluid, self-setting capability and compressive strength have been invesgated.High-purity ultrafin calcium carbonate powder was preparated by blowing CO₂ gas refine calcium chloride solution. Its average particle size is about 1.7μm and purity is about 99.7%.Wet chemical thermodynamics analysis of the preparation ofα-TCP powder was calculated in this study. A new preparing process ofα-TCP ultrafine powders has been studied in the present thesis. High-purity and ultrafine CaCO₃ powders were mixed to slurry with water and phosphoric acid is diluted to solution. The amount of CaCO₃ and H₃PO₄ was added according to Ca/P=1.51. Then CaCO₃ slurry was poured into phosphoric acid solution quickly in normal atmospheric temperature, stirring phosphoric acid solution and ultrasonic agitation. Finally, high-purity and ultrafine Ca₃ (PO₄)₂nH₂O was synthesized. Theα-TCP ultrafine powder was prepared by calcining Ca₃ (PO₄)₂nH₂O at 1260℃for 1 hour.α-TCP particle size was averagely distributed, d₅₀ was 1.35μm.The high-purity ultrafineα-TCP powder produced by the new process has excellent setting property and hydrating property. The assist agents are high-purity ultrafine DCP and CaO self-produced. Mol ratio isα-TCP: DCP: CaO =0.95: 0.025: 0.025. The mixture powders were mixed with 0.25M NaH₂PO₄/Na₂HPO₄. Their initial setting time is about 6 min, the final setting time is about 30 min. The compressive strength reached 35 MPa after 5 days immersed in Hank's solution. It was enough for repairing skull defects.By powder X-ray diffraction analysis, it was known that HA was produced in the samples. According to scanning electron microscopy observation, the fibers were well dispersed in and surrounded by the CPC. It could bond with the matrix of the bone cement.Citric acid could shorten self-setting time ofα-TCP CPC. The higher compressive strength ofα-TCP CPC block and the smaller particle size ofα-TCP powder.The study proved thatα-TCP bone cement was a new promising bone repair material.