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The aim of this study was to morphometrically analyze the tissue response to a customized pin obtained from devitalized bovine cortical bone (DBCB-pin) implanted in the subcutaneous tissue of rats, as well as to assess its microstructural aspect by scanning electron microscopy (SEM). The pins were implanted in the subcutaneous tissue of 20 rats, which were killed at 7, 14, 28 and 60 days (5 rats/period) after implantation. In the subcutaneous tissue, DBCB-pin promoted the formation of a fibrous capsule. At 7 days, capsule showed thickness of 70 ± 3.2 µm with higher density of newly formed capillaries and smaller density of collagen fibers. Between 14 and 60 days, more organized fibrous capsule exhibited smaller thickness (53 ± 5.5 µm) with higher density of fibroblasts and collagen fibers. In this period, a small and slow bioresorption of the DBCB-pin by macrophages and rare multinucleated giant cells without tissue damage was observed. The thickness of DBCB-pin resorbed was in mean only of 9.3 µm. During all experimental periods not occurred presence of immune reaction cells as lymphocytes and plasma cells. It was concluded that the pin derived from cortical bovine bone was well tolerated by subcutaneous tissue of rats and slowly resorbed could be an alternative material for membrane fixation in the guided tissue regeneration procedures.

The ideal bone graft must present biocompatibility, osteoconductive and osteoinductive properties, resistance and plasticity. Xenogenic grafts of bovine cancellous bone origin are particularly interesting due to their biologically designed porous structure that enhance both cellular and vascular invasion. The purpose of this study was to evaluate the tissue response induced by bovine macrogranular porous anorganic bone implanted in rat subcutaneous tissue. Forty rats were assigned to 2 groups, as follows: the control group received empty collagen capsules and the test group received subcutaneous implants of the test material. Samples were collected after 10, 20, 30 and 60 days and processed histologically. Histological analysis showed at 10 days a granulomatous inflammatory infiltrate, rich in multinucleated giant cells and free of lymphocytes or plasma cells, similarly to mineralized allograft implanted in rat subcutaneous. In later periods, there was a significant decrease in the inflammatory infiltrate and an increase in fibrosis around graft particles. In conclusion, the test material induced a foreign body-type granuloma with subsequent fibrosis around the graft particles implanted in rat subcutaneous and did not elicit any immune response, thus being considered biocompatible.

The treatment of persistent bone defects has encouraged the search for proper techniques or bone substitutes. In Dentistry, a common problem in the treatment of periodontal bone defects is the growth of tissues within the lesion, such as the junctional epithelium, which impair regeneration of these tissues. Guided tissue regeneration (GTR), based on the separation of the tissues by means of membranes or barriers, was developed in an attempt to improve periodontal regeneration. The aim of this study was to histologically evaluate the tissue response to a membrane of demineralized bovine cortical bone implanted in the subcutaneous tissue of rats. The study periods were 1, 3, 7, 15, 30 and 60 days after implantation. Analysis of the histological sections demonstrated a moderate to intense inflammatory response at 1 and 3 days, moderate at 7 and 15 days, and almost absent at 30 and 60 days. Resorption of the membrane began 15 days after implantation, and at 60 days only remnants could be detected in some animals. We concluded that the demineralized bovine cortical bone membrane was well tolerated by the tissues and is completely resorbed after 30-60 days by mononuclear cells and multinucleated giant cells, which disappear upon completion of the process.

The ability of a pool of bovine bone morphogenetic proteins bound to synthetic microgranular hydroxyapatite (BMPb-HA) to stimulate bone repair was determined in rat critical size defects. An 8-mm diameter defect was created in the calvaria of 25 rats. In 15 rats, the defects were filled with BMPb-HA homogenized with blood (experimental group), and in 10 rats the defects were filled only with blood clots (control). The calvariae of experimental rats were collected 1, 3 and 6 months after surgery and of the control rats at the end of surgery and 6 months thereafter. The morphometric results obtained in the radiographs showed an absence of new bone formation at 1 and 3 months post-surgery and, histologically, the defects were filled with fibrous connective tissue and numerous foci of a foreign body-type granulomatous reaction around hydroxyapatite agglomerates. At the end of 6 months, the number and size of the granulomatous foci decreased and the area of the defects was reduced by 22% compared to the 0-hour control due to the formation of new bone at their borders, although the mean area was similar to the 6-month control. We conclude that the use of BMPb-HA in the treatment of critical size bone defects of the rat skull leads to the formation of a foreign body-type granulomatous reaction that markedly inhibits new bone formation, suggesting that synthetic microgranular hydroxyapatite does not represent a good carrier for BMP-induced bone formation.