Comparative Osteogenesis of Three Clinical Bone Graft Materials. An in vivo study.

Introduction: The osteoinductive properties of a bone graft material are critical to the success of dentoalveolar reconstruction. This study aims to investigate the osteoblastic response by evaluating bone volume after 4 and 8 weeks, and osteoinductive expression markers (BMP-2 and Runx2) across three widely available graft material types (demineralized human bone matrix, mineralized human bone, and deproteinized bovine bone) using a rat calvaria model. Methods: Twenty-four (24) rats had two 5mm defects placed per calvaria. Rats were divided into 4 groups: bovine xenograft (XG), demineralized bone matrix (DBM), mineralized bone graft (MBG) and a collagen membrane control (CC) group. Within each group, samples were collected at two time points, 4 weeks (T4) and 8 weeks (T8). After 4 and 8 weeks of integration, all calvariae were scanned using a Scanco model 40 μCT. DICOM files were rendered, then analyzed using MatLab software, which produced bone volume values. Samples were fixed and subsequently demineralized for immunohistochemistry and histomorphometry. Slides were mounted and stained with H&E stain as well as BMP-2 and Runx2 markers. Number of osteoblasts expressing BMP-2 and Runx2 was counted for each group and analyzed. Results: At 4 weeks, DBM showed low mineral density (7.7%) as compared to the control (25.2%) but increased dramatically at 8 weeks (DBM, T8=27.6%; CC, T8=27.2%). Xenograft material showed an increase in mineral between T4 and T8 (XG, T4=25.0%; XG, T8=32.3%). MBG remained consistent over the 8 week trial period (MBG, T4=30.4%; MBG, T8=30.4%). BMP-2 expression was present in cells adherent to all graft materials. Runx2 expression was also observed in cells adherent to all graft materials indicating that during the 4 – 8 week healing period all materials supported osteogenesis. Conclusions: When compared to other materials, the demineralized bone matrix provided high osteoinductive properties during the 4-8 week time period based on increased mineral content. All materials were associated with immunohistological evidence of osteogenesis in the rat calvaria defect model.