Abstract:
As the human lifespan gets longer and we grow fatter across generations, our skeletons bear the wear and tear. Physical trauma as a result of accidents and conflicts are on the increase. Consequently, the need for orthopedic implants is growing without commensurate response from the local industries. This research has identified raw materials that could be processed to produce hydroxyapatite, a type of bioceramic implant. The focal point of this study is to synthesize and characterize hydroxyapatite for orthopedic applications. Calcium oxide was obtained from calcined eggshell, silica from rice husk and phosphate was mined from Ikpeshi, Akoko Edo [7.1391ºN, 6.1805ºE]. Hydroxyapatite/silica composites were synthesized by ball milling for ten hours at 350 rpm. EHA0% (Eggshell hydroxyapatite with 0% silica content), EHA5% (Eggshell hydroxyapatite with 5% silica), EHA10% (Eggshell hydroxyapatite with 10% silica) and EHA15% (Eggshell hydroxyapatite with 15 % silica) synthesized powders were pelletized with a hydraulic hand press. The pellets were sintered at 900c and cooled at 5ºC per minute down to 250ºC. The sintering schedule was a two-step format from ambient temperature to 500 ºC at a rate of 1ºC per minute and soaking time of 60 minutes. The second step provided a continuous heating to 750, 800, and 850 ºC respectively at a rate of 5 ºC per minute and soaking time of 120 minutes. FTIR of the synthesized powder confirmed the emergence of carbonated hydroxyapatite in broad band 500 to 3500 cm-1. The FESEM micrographs displayed fine nano powder as confirmed by the Xpert high score software of the XRD. The XRF divulged detailed elemental analysis of the composite containing calcium, phosphorus, oxygen and silicon in varying percentages. The Ca/P molar ratio ranged from 1.21 for EHA5% to 1.68 for EHA0% compared to the standard of 1.67. The peaks of the EDS analysis at P, O and Ca gave credence to results of the XRF. The FESEM micrograph of EHA10% in simulated body fluid showed optimum bioactivity with flower-like apatite growth. The relative density, open porosity, diametral tensile strength, compressive strength, pH, linear shrinkage (diameter), linear shrinkage (thickness) of the sintered hydroxyapatite were measured using the appropriate tools and equipment. The results fell within the various tolerable ranges obtained from measurements of the average human bonnes. The synthesized hydroxyapatite therefore was considered viable for orthopedic applications.
