Histologic and histomorphometric evaluation of anorganic bovine bone (ABB) retrieved 7 years after a sinus augmentation procedure

Background Anorganic bovine bone (ABB) has osteoconductive properties and no inflammatory or adverse responses. In spite of these successful results, histological data in humans over the long-term period are scarce. The purpose of this study was to evaluate a bone specimen retrieved from a sinus augmented with ABB 7 years after surgery. Materials and methods The histological examination was performed in 5 thin sections of the specimen, comparing histomorphometric measures for newly formed bone, marrow spaces, residual ABB particles. The investigation was carried out under light microscopy. Results Trabecular bone with many remodeling areas was present. Grafted ABB particles were almost completely surrounded by bone, and in some cases they were found to be in contact with secondary osteons. Some particles were united by newly formed bone trabeculae. In other areas, the particles seemed to be almost completely resorbed and substituted by bone. No gaps were present at the bone-biomaterial interface. No inflammatory tissue infiltrate was present. Histomorphometry showed that bone represented 46%±3.8%, ABB particles 9%±1.2%, marrow spaces 45%±3.2%. Conclusions After 7 years the tissue pattern appeared composed of residual particles of the grafted biomaterial in close contact to the new bone. The mineralized matrix of the bone around the particles had collagen fibers randomly oriented and significantly more osteocytes embedded. The results demonstrate both a high level of osteoconductivity and a "biomimetic" behaviour of the biomaterial over time.