| Defect and injury of bone is a common disease that badly affects sufferer'shealth. In order to improve therapy effect, the development of bonerepair/replacement materials that is analogous to human's bone is naturally veryimportant both in medicine and biomaterials. Porous HA/β-TCP biphasic ceramics is a highly biocompatible material. Theporous structure of ceramics is very important for its biological properties. It hasbeen reported in vivo that the use of porous HA/β-TCP promotes the bone ingrowth(osteoconduction) and has the possibility of acquiring ectopic osteogenesis(osteoinduction) with appropriate critical geometry of macroporosity. Recently it hasbeen proved that the volume of bone ingrowth at initial stage is primarily dependenton interconnectivity. The interconnections of pores and the large number ofmicropores on pore wall of HA/β-TCP biphasic bioceramics play an important roleon bone recolonization. It has been hypothesised that an ideal implant macrostructuremay be similar in morphological characteristics to the inorganic matrix of the bone. Preparation methods of porous ceramics strongly influence their physicalproperties and microstructure, which lead to different bioactivity. In present, almostall researches are carried out to obtain a good method that can control pore structureand physical characteristics. Aiming at difficulties of common methods in controllingceramics' pore structure, a study was carried out in order to find a novel preparationmethod or improve present preparation method of porous ceramics with good pore - iii -structure and bioactivity. In the present thesis, a novel method was described how to prepare the porousHA/β-TCP biphasic bioceramics. The main process was: the ceramic porousstructures were formed by using hydrophilic crossinked polyurethane foams withlarge amounts of aqueous slurry of biphasic calcium phosphate ceramic powderwhile was reacting a particular isocyanate capped polyoxyethylene polyol. A foamstructure was attained in this reaction. The resulting foams with ceramic powderuniformly distributed throughout were sintered at temperatures 1150℃ holding 3hours for preparing a rigid porous ceramic. 3∶10 (W/W) of the amount ofpolyurethane to ceramic slurry with 35% solid state content by weight is favorable.The sintering conditions strictly influenced the properties of porous ceramics. 90℃/hour-heating rate before 700℃, holding 1 hour at 240℃ was favorable in furnace.Porous HA/ β -TCP biphasic bioceramics with 67.5% porosity,100 ～ 800μmmacrospore size, a large number of micropore distributed in inside surface of poreand high degree pore interconnectivity could be attained via this method. The effects of materials and techniques (such as heating rate, sinteringtemperature, sintering time and so on) on ceramics' structure and properties werestudied carefully. It was found that a higher sinter temperature results in a higherstrength but lower porosity. A pure HA/β -TCP phase was obtained at sinteringtemperature of 1150℃ and β-TCP phase was absolutely change to α-TCP phase atsintering temperature of 1200℃. Meanwhile heating rate before 700℃ needed to beas slow as possible with a rate limitation of 90℃/hour in order to obtainedappropriate mechanical properties. Dissolution of the prepared ceramics was also studied and dissolution kineticequation was obtained as -ln(1-x)= 0.54t0.85, indicating that the ceramics had a gooddissolution and comparatively higher initial dissolution rate. Meanwhile it was foundthat carbonate hydroxyapatite(CHA) could be formed within surface where is 4mmdistant from exterior surface of ceramics when ceramics was immersed in swayingsimulated body fluid. |
