Long-term evaluation of maxillary reconstruction by iliac bone graft

The aim of this study was to analyze histologic and immunohistochemical modifications taking place in maxillary sites reconstructed by iliac crest bone grafts, 4 months (T1) and 10 years (T2) after grafting, in comparison to native iliac crest bone (T0).By light microscopy, T1 samples showed well-organized osteoblasts and extracellular matrix (ECM), and surrounding areas of connective tissue where a discrete number of blood vessels can be distinguished. Samples obtained from reconstructed areas after a long period of follow-up (T2) were characterized by uniform mineralized ECM with cavities containing osteocytes, whereas T0 samples disclosed both mineralized matrix and bone marrow. Matrix metalloproteinase 2 (MMP-2), vascular endothelial growth factor (VEGF), inducible nitric oxide synthase (iNOS), and bone sialoprotein (BSP) expressions were investigated by immunohistochemical analysis. Both MMP-2 and VEGF showed significantly increased expression in T1, with respect to T0, and lowered in T2. Otherwise, BSP expression, which was elevated in native iliac crest bone (T0), was deeply decreased in T1 and T2 samples. Moreover, changes in iNOS expression and in apoptotic cell nuclei percentages (TUNEL analysis) seemed to have a similar trend, increasing in T1 and lowering in T2.After a period of 4 months, iliac crest bone graft-reconstructed sites show mineralizing nuclei not strongly represented, as suggested by BSP lower expression, whereas new blood vessel proliferation and active remodeling phenomena are developing. After a long period from the grafting (T2), BSP expression decreases along with MMP-2, VEGF, and iNOS, suggesting the presence of only weak arrangement phenomena of the graft.