The production of bone bio-grafts and in vivo/in vitro biocompatibility-bio mechanical analysis

The latest advances and applications involving adaption of medical science with materials and Bioengineering has brought about many innovations. The new generation of biomaterials now make it possible to repair and change the functional tissues of the human body. Because of the biocompatibility of Hydroxyapatite which is based on calcium phosphate, it can be used to repair cracks, deformed and broken bones. It can improve the integration of bone-implants and can be used as a coating material. Because of the similarity between the properties of bone tissue and the mechanical properties of hydroxyapatite (HA), it?s strength properties which are similar to the chemical structure of hydroxyapatite-based bone, can be used to improve the sucess of grafts. The expected properties of a biomaterial are: biocompatibility, specific mechanical properties, porisity, and to be light enough to have the ability of allowing cellular nutrition. In this respect, artificial graft materials have a major significance because of what they offer for a success in terms of biocompatibility as well as low cost.This study is divided into four main groups. In Group I: Ca(NO3)2.4H2O, phosphoric acid was used to produce more econonomical HA which is the main component of bone material derived from commercial HA. In order to examine the effects of pH on gelation, sintering and mechanical properties, gel grafts were produced at different temperatures. The mechanical and morphological effects of pH produced grafts were then studied. When the compound HA was in a gel form the pH value was changed from 12 to 5, 7, 9 by adding a NH4OH buffer solution. In Group II; HA based ceramics was fabricated by using the biocompatible inorganic chemicals e.g CaO, KH2PO4, P2O5, Na2CO3.The effects of the differences of the pH was investigated on HA. Hydroxyapatite ceramics enhances sinterability, bioactivity and biocompatibility were produced without separating the components of the HA. This included adding Na2CO3, CaO, KH2PO4, P2O5. Material additives were selected from the mineral components of hard tissue and bioactive glass (CaO) to increase sinterability. After phase diagrams were studied, the materials added to HA (such as CaO-P2O5), were chosen according to their physicochemical properties.In vivo experiments concerning grafts produced by the sol-gel method were performed using New Zealand rabbits to examine the effects on repaired or damaged bone tissue. The grafts produced in Group III were obtained by the addition of cuttle fish, sepiyolit, and egg shell powder and were granulated at different rates. The particle sizes were studied in regards to the effects on sinterability, morphological and mechanical properties. In Group IV; the alternative bio-grafts which contained HA, sepiyolit, cuttle fish and bioglass based CaO, KH2PO4, P2O5, Na2CO3 and gelatin were produced by using the sol-gel method to examine the effects of the porosity in the porous graft materials. Alternative bio-grafts were produced in Group IV and compared with bio-grafts in Groups II and III. All study produced bio-grafts were compared with commercially available graft material as well as the control group. XRD and FTIR analysis was performed in regards to the effects on chemical properties and phase transformations of the bio-grafts which was obtained by the introduction of additives to HA to increase the sinterability. SEM analyzes were used to show the changes of the structural morfological. Sintered materials were added (Ca / P ratio to be 1. 67) to study the effects of densification, phase composition, grain growth and fracture behavior of HA.As a result of the study, the results presented in Group I, FTIR, and XRD show that HA was produced by using Ca (NO3) 2.4H2O, and phosphoric acid. When the pH value was changed in the 5 to 12 range, it was noted that the pH differences changed the morphological and mechanical properties of the graft. Along with lowering the value of the acid concentration, it should be noted that the gaps between the grains decreased and showed an increase in graft sinterability. When the pH value was 5 no gaps between the grains were observed. As a result of the decrease in the pH value, it was shown that the brittleness of the graft increased and the mechanical properties decreased. KH2PO4 which was added in HA did not increase the densification of HA but Na2CO3 caused an increase in densification of HA. It was determined that the Yttria compound be added to HA to increase the hardness and compressive strength of HA. This is the result of in vivo and in vitro experiments found in Groups I and II. It was shown that the bio-grafts that were used to fill defects acceleraterated the healing of bones more than that of the control group. The results of in vivo and in vitro experiments of the bio-grafts produced with the sol-gel methods were found to be close to the commercial graft. However, by adding CaO and Yttria in HA increased the bone defect repair, and it was demonstrated from in vitro and in vivo experiment that the produced bio-grafts did not show any toxic effects. In Group III, the first time, biografts was produced by the addition of natural products into HA. Different rates of cuttle fish back bone, eggs shell and sepiolite generally increased the sinterability and so mechanical properties. In Group IV, this study attempted to obtain a porous structure by adding different amounts of gelatin into HA, cuttle fish bone and sepiyolit-based bio-gelatin. The porous structure have been obtained and was examined in regards to the effects on the mechanical properties of the graft. From SEM analysis, It was demonstrated that the amount and diameter of pores increased with the increased amount of gelatin.