Preparation And Property Of Biodegradable Calcium Phosphate Glass-ceramics

Calcium phosphate glass-ceramics are widely used as bone replacement materials for their chemical composition and biological property are similar to bone mineral. The demanding of the biodegradation property is variational with the position and replacement condition. Calcium phosphate glass-ceramics are considered to be one of the most significant potential bone replacement and drug delivery materials for the controllable chemical constitution, structure, mechanical property and degradation.In this study, the porous glass-ceramics were obtained by dipping polymer foams into slurry including the glass powder of CaO-P₂O₅-B2O3-Na₂O (CPBN) prepared by melt-quenching method. The glass constitution, crystallization from glass matrix and microstructure were analyzed by FTIR, DSC-TG, XRD and SEM. The CaO-P₂O₅-ZnO-Na₂O (CPZN) and CaO-P₂O₅-SrO-ZnO-Na₂O (CPSZN) glass-ceramics were prepared by sol-gel method. The influence of ZnO, SrO and heat treatment to the phase constitution and microstructure of the glass-ceramic were also investigated. The biodegradation of the CPBN, CPZN and CPSZN were performed in phosphate buffer solution (PBS) and stimulated body fluid (SBF) respectively to determine their biological activity.The result indicated that fiber grainsβ-Ca(PO₃)₂ consisted of nano spherical particles are deposited in the CPZN glass matrix by heat treated at 800℃. The compressive strength of the porous bodies was in the range of 2.25～3.27MPa while porosity was 60～70%. By soaking in SBF solution for 3 days, some spherical crystalline hydroxyapatite (HA) detected by energy dispersive X-ray analysis (EDXA) were precipitated regionally on the surface of the specimens, this result implied that the CPBN porous glass-ceramics have good biological activity.Porous bodies of CPZN and CPSZN glass-ceramics prepared by sol-gel method and following heat treatment consisted of glassy struts and macropores with crystallineβ-Ca₂P₂O₇ and Na₂CaP₂O₇ phase precipitates immersed in the residual glass matrix of the wall of pores. Homogeneous nanometer Ca₄P₆O₁₉ grains were crystallized from glass matrix after heat treatment at 750℃. By soaking the sample in PBS solution for 11 days, the concentration of calcium ion reached peak value and then a severe decrease was observed for the dynamic equilibrium between dissolution speed of Ca²⁺ and deposition speed of HA-like according to the SEM micrographs of the deposited HA-like after soaked for 11days. By soaking in SBF for 7 days, a layer of HA was dispersive on the surface randomly. For CPSZN system,the concentration of Ca²⁺ was decreased after soaked in PBS for 7 days. The HA-like and Sr-HA was observed after soaking in PBS for 7 days. By soaking the sample in SBF for 3 days, the material was covered by HA-like and Sr-HA, which indicated that the additive of SrO could improve biological activity.