| Calcium phosphate cement is considered as the promising bone repairing materials due to its excellent biocompatibility, osteoconductivity and remodellability. However, its clinical use requires on site powder-liquid mixing, which prolongs surgical time and worsens graft properties, and it is desirable to develop a new type premixed CPC to satisfy the clinical require.Objective:In this paper, puttied premixed CPC pastes were prepared by combining cement liquids comprised of glycerol or polyethylene glycol with CPC powers that contained beta-tricalcium phosphate (β-TCP) and monocalcium phosphate monohydrate (MCPM). The effects of preparing conditions including powder to liquid ratio, particle size on washout resistance, setting time and mechanical properties of the premixed CPCs were investigated. The biocompatibility was evaluated by implanting the premixed CPCs into the subcutaneous site of rabbits and epiphyseal and metaphyseal, cylindrical bone defects of sheep.Methods:1 subcutaneous implant 16 rabbits were randomly divided into 4 groups according to the observation time, each with four. The experimental materials and control materials were implanted in the rabbits abdominal subcutaneous on both sides, pathological conditions were observed after two weeks, four weeks, eight weeks,12 weeks (2 W,4W,8W,12W).2 Bone defects 9 healthy sheep were randomly divided into three groups according to observe the time, each with three. Sheep femoral condyle were drilled into two holes of 04×12mm size from the outward towards the inner on both sides, the holes were filled by pre-mixed calcium phosphate cement or reference material, pathological, X-ray and bone mineral density were observed after two months,4 months and 6 months (2 M,4M,6M). Experimental material included PG-CPC and the PP-CPC; commercial hydroxyapatite cement (A-CPC) was control material.Results:1 the results revealed that the CPCs have a good biocompatibility for moderate inflammatory responses were observed, and its intensity declined in company with the thickness of bursa around and CPC implants gradually degraded with time. However, according to the GB/T16886.1-1997 for bioiert material, control material apatite CPC was rated as grade two whereas the premixed CPCs was assessed as grade three on both capsule reaction and inflammatory cell response. The full degradation of premixed CPCs was presumed after about 24 weeks whereas control apatite CPC showed very limited resorption behavior. 2 The premixed CPCs were implanted in epiphyseal and metaphyseal, cylindrical bone defects of sheep, using the aptite CPC as control. The results of histological evaluation, radiographs and bone density tests revealed that the two premixed CPCs showed the highest new bone formation and least CPC remnants at 6 months, whereas the control apatite CPC was almost unchanged over all time periods.Conclusion:1 The continuous resorption of premixed CPC implants might have aroused the inflammatory reaction, which might be the major reason of differences in capsule reaction and inflammatory cell response between experimental materials and control material.2 The value of bone density in experimental CPC materials gradually close to the bone density of the surrounding tissue with the extension of implantation time, the alteration and reconstruction process was almost complete in the defect site six months after implantation, mature trabecular bone structure was fully formed. However, the control material A-CPC always maintained the original value of BMD, almost no obvious degradation was observed in the period of 6 M implantation, the results were also confirmed by the X-ray and bone mineral density (BMD) tests. |
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