Bone Augmentation Potential in Rabbit Calvaria and Ex Vivo Cytotoxicity of Four Bone Substituting Materials

Background and aims. Tricalcium Phosphate (TCP), Bovine-Derived Hydroxyapatite (BioOss™), Demineralised Freeze-dried Bone Allograft (DFDBA) and Calcium Sulphate (CaS) were compared in vitro for osteoblast cytotoxicity and in rabbit’s calvaria to measure the bone histopathologic response. Materials and methods. 34 critical size defects in the calvaria of 12 male Australian rabbits were randomly filled with the materials and 2 empty defects were used as controls. After one month, histologicalal evaluation was performed on the samples to record regenerated bone type and volume, material absorption and the amount of inflammation. Saos-2 cell line was exposed to the materials and the cell line vitality was tested with Methyl Tetrazolium Test (MTT) to determine material’s osteoblast cell cytotoxicity. Results. The type of regenerated bone did not show a significant difference between the groups (p=1.0) while the amount of bone inflammation was significantly different (p=0.021), where BioOss caused the least and DFDBA had the highest. Bone formation was also similar between the groups (p=0.428). DFDBA group showed the highest material absorption while TCP group had the lowest (p=0.028). DFDBA was associated with significantly higher Saos-2 cell line viability than TCP and Bio-Oss that were significantly less cytotoxic comparing to CaS (p 0.0001). Conclusions. DFDBA group had the highest amount of material absorption and was associated with more inflammation than other materials in the rabbit calvaria. BioOss exhibited lowest amount of inflammation and TCP had the lowest amount of material absorption. Results of cytotoxicity test might be affected by different solubility constants of the test materials.