Creation and validation of animal bone models to simulate human bone density classes for implant placement experiments: 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 were correlated with Misch's density classification scheme (D1-D5) and with the density and cortical classification of Al-Ekrish. RESULTS: Only the mandibular ramus of pigs met the specifications corresponding to human bone quality types D1/D2. Bone quality type D2 was observed in the bovine iliac crest and femoral heads, with HU in the lower range and cortical thickness not exceeding 2mm. The inner areas of the bovine rib had an average bone density of 350-700 HU and a cortical thickness of 1.5mm, corresponding to type D3. The average density of the part of the bovine rib farthest from the spine ranged from 160 to 345 HU, corresponding to bone quality type D4. Only the porcine rib and femur fell within the density range represented by bone quality type D5, with an HU of 0-150. CONCLUSIONS: To ensure high accuracy, the HU and compacta thickness for each bone segment used for in vitro implantation research should be determined using a CT device, as the bones of each specimen are different, just as they are in humans. If only an approximate reference is necessary for in vitro experiments, the classification of animal bone regions into different density values, as demonstrated in this study, is appropriate.