Hydroxyapatite-perlite composite biomaterial production, characterization and in vitro behavior

Nowadays, the application areas and importance of biomaterials, which are used as an improvement or replacement of a living tissue or an individual part of the human body with continuously or interruptedly contact with body fluids, have been gradually increasing. One of the bio-ceramics, hydroxyapatite, which is mostly used in the biomedical field, is a calcium phosphate compound and it is shown as Ca10(PO4)6(OH)2. Hydroxyapatite materials are a very popular material used in bone repair because it accelerates bone growth in the implant surroundings. Hydroxyapatite can be obtained by both synthetic and natural methods. Synthetic hydroxyapatite biomaterials are highly reliable; however their production is complex and expensive. Naturally HA produced biological apatite is both easier and more economical to produce. In this study, synthetic HA and natural HA obtained from sheep bone were used as matrix. Composites were prepared in three groups. In group I; both synthetic hydroxyapatite matrix and sheep hydroxyapatite matrix were prepared by adding 1, 3, 5, 7, and 10 weight % expanded perlite reinforcement. The expanded perlites added in order to compare grain size were used in three different sizes of 50, 75 and 100 microns. In group II; the same two different matrices were added with 5 weight % TiO2 in order to increase the mechanical and physical properties, additionally, all composites were added with 5 weight % MgO and P2O5 in order to increase the physical properties and improve the bony structure and increase the biocompatibility. TiO2, MgO and P2O5 are kept fixed at 5 weight % in all samples in this group. In addition, composites were added as 1, 3, 5, 7 and 10 weight % expanded perlite reinforcement. The expanded perlites added in order to compare grain size were used in three different sizes of 50, 75 and 100 microns. In group III; the same two different matrices were added with 5 weight % ZrO2 in order to increase the mechanical and physical properties, additionally, all composites were added with 5 weight % MgO and P2O5 in order to increase the physical properties and improve the bony structure and increase the biocompatibility. TiO2, MgO and P2O5 are kept fixed at 5 weight % in all samples in this group. In addition, composites were added as 1, 3, 5, 7 and 10 weight % expanded perlite reinforcement. The expanded perlites added in order to compare grain size were used in three different sizes of 50, 75 and 100 microns. Prepared samples were mixed with electronic mixer for 30 minutes each sample. Pellets with a diameter of 11 mm were formed with a cold press with a pressing pressure of 25 MPa. The All samples were sintered at 900 oC for 1 hour at a sintering rate of 5 oC /min. The all samples were applied analysis is such as density, micro-hardness test, X-ray diffraction, scanning electron microscope (SEM) and EDX. Also, the samples were kept in the synthetic body fluid and their in vitro behavior was observed. The micro-hardness of the expanded perlite increased with both the percentage by weight and the grain size rise. Sheep HA composites micro-hardness showed higher values than synthetic HA composites. The highest micro-hardness value was determined as 302 HV. As the amount of expanded perlite reinforcement increased, micro-porous and rough structures were observed. The hydroxyapatite structure was observed in sheep HA matrix composites. Synthetic HA composites were observed to have more apatite structure on the fifth day in vitro. However apatite formations were observed to occur on the surface of sheep HA composites on the first day. It was also observed that the formed apatite structure increased with the increase of the waiting period in the synthetic body fluid (SBF). As a result, the use of expanded perlite as a bio-ceramic material is promising. It is also thought that this work should be developed.