Processing of calcium phosphate porous materials by "self-setting"

Macroporous biornaterials based on (x-tricalcium phosphate (alpha-TCP) bone cement with porous structures suitable for implantation purposes were prepared in the present work. According to the reversible swelling/deswelling behavior of gelatin at a single temperature or pH, a "self-setting" method that uses gelatin granules as pore formers was developed to process the porous microstructure. By mixing gelatin powder and bone cement powder (BCP), and adding water (1 solution of (NaH2PO4HO)-H-.) to form pastes which set within 15 to 30 min, this setted cement was then immerged in deionized water of temperature 25degreesC or 32degreesC for hydration. During the hydration, the pH of deionized water after cement pastes were introduced at 32degreesC changed from 8.6 to 7.2 which caused by the transformation of (alpha-TCP to hydroxyapatite (HA). Meanwhile, gelatin particles will swell by water uptake to form large size spheres in cement matrix. This swelling behavior is sensitive to the variation of pH value. After hydration for 4 day, a body containing gelatin gel spheres was obtained. Then heating the deionized water to temperature 50degreesC, gelatin spheres in cement matrix were solved and porous microstructure composed of larger pore sizes corresponding approximately to the average size of the swelling gelatin granules was obtained. The porous bodies by this technique were found to have tractable and interconnected porosity in the range of 60similar to84%, with typical pore sizes ranging from 100similar to300 microns. This new processing technique can be used in the manufacture of unsintered biomaterials.