Long-term evaluation of autologous extraoral bone grafts as bone substitute in maxillary vertical augmentation: An immunohistochemical study

The aim of this study was to evaluate calvarial grafts when used as bone substitute for maxillary vertical augmentation prior to dental implantology. Bone specimens were harvested from patients at T0 (time of bone harvesting), 4 months (T1), 6 months (T2) and 15 years (T3) after grafting procedure. Morphostructural analysis and immunohistochemical analyses of boneseialoprotein-2 (BSP2), Collagen I, Vascular endothelial growth factor (VEGF), ERK ½ and nitride oxide (iNOS) inflammatory protein, expression were carried out. Outcomes from T0 specimens were compared to T1, T2 and T3 samples. In immunohistochemical analysis T1 and T2 samples showed the presence of important remodeling phenomena, with areas of bone resorption and apposition, together with new blood vessel formations. The T3 sample showed morphological features very close to native bone, as shown by the disappearance of welding lines. However, small polygonal cells resembling osteoblasts were close to Havers channels. Immunohistochemical analyses showed a drastic decrease of Collagen expression, at T1 and T2, stabilized at T3, in parallel to BSP2 expression increase, which was, however, considerably reduced at T3. Moreover VEGF angiogenic factor was increased at T2, in respect to T0, T1 and T3 which are quite similar. The highest level of Erk1/2 is evidenced in the T2 sample, basal levels of iNOS, related to inflammatory events is highlighted in T0 and T3, in respect to T1. Thus, autologous calavarial bone grafts seem to be suitable as biomaterial for bone regeneration procedures of the jaws. Moreover, the used protocol could be useful for studying bone substitutes in oral surgery and implantology.