Influência das matrizes mineralizada e desmineralizada de enxertos ósseos bovinos no reparo de defeito ósseo intrabucal em ratos

Abstract

Mineralized bovine bone grafts are one of the most commonly used alternatives in dentistry to promote replacement of bone loss. Recently, the use of demineralized bone grafts has been investigated since collagenous and non-collagenous proteins may contribute to the osteoinductive potential of xenografts. The present study evaluated the bone repair of an intraoral defect in rats submitted to grafting with a national bovine bone (Lumina Bone-Critéria) in its commercial (mineralized) version and in a Demineralized version processed in the laboratory. The imported graft, Bio-Oss®, was selected as a positive control, since it is the xenograft of greatest reference in the literature. Prior to the grafting procedures, the demineralized biomaterial was evaluated with histological and immunofluorescence techniques to verify the preservation of matrix proteins after the demineralization protocol. Immunofluorescence results of type III collagen, osteopontina and BMP-4 showed that demineralization in 10% EDTA does not compromise or destroy organic components of the bone matrix. Hence, the grafting protocols proceeded. Bone defects were filled with: 1. Mineralized bovine bone (MBB); 2. Demineralized bovine bone (DBB); 3. Bio-Oss® bovine bone (positive control) (BO); 4. Blood clot as negative control (NC). After 1, 7, 14, 21 and 49 days, the samples were processed for macroscopic, radiographic and histological analysis. The macroscopic analysis showed a satisfactory gingival healing at the surgical site for all groups, with no difference among the grafts used. At 14 days, the mucosa over the operated area was closed with no statistical difference among the groups. The radiographic assessment demonstrated higher radiopacity at 49 days in the bone defects grafted with DBB. The histomorphometric analysis stained with Masson’s trichrome and PicroSirius Red and later submitted to Image Jey software revealed, respectively, higher trabecular deposition and greater bone maturation in animals of the DBB group. The bone defect filling was completed at 49 days. Also at 49 days, the pattern of bone deposition in the NC group seemed incomplete and, in some of the defects, revealed a concave surface on the superior border of the bone in the surgical site. This suggests a loss of bone volume in comparison to the other grafts under study. Histological analysis revealed that both mineralized grafts, Lumina Bone mineralized (Critéria) and positive control (Bio-Oss®) exhibited organic residues inside the granules, what is in unconformity with the chemical composition (99,9% inorganic) reported by the manufacturers. In both groups, histological results presented inflammatory sites up until the 14th day amongst the grafted granules, mainly in a most superficial area (cervical third) of the bone defect. Contrastingly, inflammatory response for groups DBB and NC at 14 days were in cessation. Areas of mineralized granules and native bone in a rejection process were seen in both mineralized groups, which were often located in the margins of the defect. Reabsorption analysis of the grafts through time revealed that DBB presented a fast and complete reabsorption. BO exhibited higher resistance to being reabsorbed followed by MBB. At 49 days, most mineralized grafts emained inside the surgical site with granules osseointegrated to the basal and medial thirds of the defect. In conclusion, the present study provides for the first time histological and radiographic data on the national bovine bone graft (Lumina Bone) in mineralized and demineralized versions where the DBB provided enhanced results. The osteoinductive potential of the aforementioned graft must be further investigated via different methodologies in distinct critical sized defects with the purpose of securing it as a viable therapeutic strategy.