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IMPROVEMENT OF BIOGLASS REINFORCED HYDROXYAPATITE COMPOSITES

Materials that can substitute the bone are named as implant materials. Hip, knee, teeth prothesis,heart valves are all examples of implant materials and are called biomaterials. Biomaterials, which have had the greatest developments in the last 30 years, can be based on either on metals, ceramics, polimers or composites.

The purpose of improving composite materials is that composites can exhibit properties that a material can not inhibit just by itself. Hydroxyapatite shows good biocompatibility with the body but can noy used at load bearing parts in the body due to its low mechanical properties. Bioglasses that have been developed by Hench about 30 years ago, exhibit both good biocompatibility and bioactivity. The combination of HA and bioglass provides better mechanical properties without the formation of any toxic reaction.

In this study the mechanical properties of hydroxyapatite containing 2.5, 5 and 10% bioglass (45S5) which were sintered at different tempatures was investigated. First of all hydroxyapatite obtained from extracted human teeth was mixed with 2.5, 5 and 10% bioglass respectively. After compaction they were sintered 1100, 1200 and 1300 ºC for four hours. In order to find the optimum sintering tempature, microhardness, density and compression tests were carried out and the materials were characterized by scanning electron microscopy and X-ray analysis.

By the bioactivity characterization, specimens were kept in a simulated body fluid for maximum 4 weeks and compared to normal bone tissue. The optimum results were obtained with the specimen containing 10wt% Bioglass and sintered at 1200ºC with 383 HV average microhardness, d=2.72 g/cm3 average density and σavr= 83 MPa compression strength. The improvement of the mechanical properties can be explained by the new occuring Ca5(PO4)2SiO2 based phases. Moreover, with increasing the sintering tempature to 1300ºC the formation of the phase Na2HPO4.7H2O lowers the mechanical properties.