Biocompatibility Evaluation of Different Granular Porous Anorganic Bovine Bone Grafts

Objectives: Different processing protocols could be used to producing xenografts. It is essential to evaluate the biocompatibility of biomaterials obtained before the clinical use. Apatite-based xenografts produced by four different routes were investigated by in vitro and in vivo biocompatibility testing. Methods: Cytotoxicity was determined by indirect contact (ISO 10993-5), DMEM without the biomaterials extract and titanium degree 2 were used as negative controls and phenol 0.2% as positive control. Fibroblasts Balb/c (3x10⁴/cm²) was treated with serial dilutions of crude extracts for 24 hours of developing materials A, B, C and D, when the cells were detached for counting. In the second level test (ISO 10993-6), 50 mg of each xenograft (two under development (A and B) and a commercial product available in the wide world market (C)) were placed in subcutaneous tissue of mice (n=30). The animals were killed after 1, 3 and 9 weeks and submitted to histological processing for light microscopy analysis. Results: Biomaterials crude extract killed 15 to 20% of the cells comparing to control (p<0.05, ANOVA), however there was no difference among the biomaterials processing routes (p>0.05). Histological analysis showed at 1 week a mild inflammatory infiltrate in response to the C and a moderate response to A and B, particularly near the most irregular regions. Mild fibroblastic and angioblastic proliferation were detected around the grafts particles. In later periods, there was a significant decrease in the inflammatory cells and an increase in foreign body multinucleated giant cells and fibrosis around graft particles of all biomaterials. Blood vessels were also observed, confirming the process of angiogenesis around the implants particles. No differences among the materials were observed after nine weeks. Conclusions: the tested biomaterials were biocompatible and its behavior and osteoconduction potential should be evaluated in bonny defects.