Development of porous hydroxyapatite for orthopedic applications

Hydroxyapatite (HA) is a calcium phosphate based ceramics which is known to be one of the most important implantable biomaterials due to its biocompatibility and osteoconductive properties. Porous HA implants have been used as substitutes for hard tissues in the clinical applications. The current work describes the synthesis of hydroxyapatite [Ca10(PO4)6(OH)2] by the solid state reaction of â- tricalcium phosphate (â-TCP) and calcium hydroxide [Ca(OH)2]. Both the chemicals were taken in the molar ratio of 3:3 and were sintered at two different temperatures for different time periods. For one sample, sintering was carried out at 1000oC for 8hours and for the other one at 1150oC for 2hours. The phase purity of both the samples was determined by XRD analysis and for 10000C higher phase purity was obtained. Then pellets of hydroxyapatite with 0% and 30% porosity were synthesized by implementing three different pore formers (starch, wheat flour and coffee) while sintering. The porous pellets were characterized in terms of mechanical and biological properties. Apparent porosity, bulk density, linear axial shrinkage, linear radial shrinkage and volumetric shrinkage were determined. Biodegradation study was carried out in Tris-HCl buffer solution at 370C having a pH of 7.4 by soaking the samples in the solution for 21 days. At the end of 21days, the final weights of the samples and change in pH of the solution was observed. From the observations the % weight loss was determined and release of calcium and phosphate was confirmed due to the increase in pH of the solution