Biological Evaluation of a New Biogenic Hydroxyapatite

Key words: biogenic hydroxyapatite, biomaterials, biocompatibility, bone replacement material       
The replacement of damaged bone tissue at various body areas constitutes a challenge.  Many different biomaterials have been selected for this end, such as metals, polymers, ceramics and hydroxyapatite. The aim of this study was to evaluate locally the biological properties of a new biogenic hydroxyapatite (bHA) synthesized at our laboratory, using implant test ISO 10993-6 in tibia bone marrow of rats. Methods: cortical bone marrow cavities were performed on tibias of 32 male Wistar rats (200 g + / - 20 g). The animals were divided in 2 groups, a Control Group (CG) was implanted with zinc oxide and eugenol-based cement (IRM), and an Experimental Group (EG) was implanted with bHA. The results were histologically evaluated at 7 and 21 days after surgery. Results: CG: hemorragic fibrin exudation and mononuclear cells infiltrated with granulation tissue were observed at both evaluation periods. No bone at the material-tissue interface was observed at either of the evaluation periods. Also, a proteinaceous eosinophilic material was deposited around IRM particles. EG: moderate exudation and infiltration inflammatory reactions were observed at both evaluation periods. At the material-tissue interface, bone formation was moderate at 7 days and intense at 21 days post-implantation. Conclusion: the bHA did not produce local toxicity and is biocompatible and bioactive. These results support proceeding with the bHA evaluation by usage test, recommended by ISO International Standards Rules, in order to evaluate its use as a bone replacement material.