Creation and validation of animal bone models to simulate various human bone densities: An ex vivo study

Background: Various experimental models are used to evaluate the primary stability of dental implants. A synthetic bone lacks the trabecular structure, while the quality of ex vivo animal bones is very different. This study aimed to identify ex vivo animal bones with bone density and cortical thickness that correspond to those of human bone.Methods: Porcine and bovine bone fragments from different regions of the animal body were examined using computed tomography (CT). Hounsfield units (HU) in the inner bone and the thickness of the cortical layer (< 1 mm: thin layer; ≥ 1 mm: thick layer) were correlated with Misch’s density classification scheme (D1–D5) and a modified classification scheme of Lekholm and Zarb. Results: The following types were found: Type 1 (entirely cortical bone, D1): porcine mandibular ramus; Type 2 (thick cortical bone) 2a (dense trabecular bone D2): bovine femoral heads; 2b (medium dense trabecular bone, D3): scapula or processus spinosus of pigs and thick bovine ribs; 2c (low dense trabecular bone, D4): thin bovine rib farthest to the spine, bovine scapula, and porcine iliac crest; 3 (thin cortical layer); 3a (dense trabecular bone): bovine iliac crest with a thin cortical layer; 3b (medium dense trabecular bone): inner part of the bovine processus spinosus; and Type 4 (thin cortical layer and low dense trabecular bone, D5): porcine femur. Conclusions: The HU and compacta thickness for each bone segment used for in vitro implantation research should be determined using a CT, as the bones of each specimen are different as in humans. If an approximate reference is necessary, the present classification of animal bone regions into different types might be appropriate.