LA RIGENERAZIONE OSSEA DOPO INSERIMENTO DI ALLOINNESTI: RUOLO DELLA VASCOLARIZZAZIONE

Following tooth loss patients may require prosthetic rehabilitation and/or dental implant insertion. A successful implant rehabilitation needs on a sufficient volume of alveolar bone that could be not available in all patients so, surgical procedures of bone augmentation are sometime required. The tecnique of “bone regeneration” using bone graft is widely used to repair small and medium sized bone defects representing an auxiliary medical therapy for endosseous implants insertion. Bone grafts are organic or inorganic components used to substitute, induce or increase bone formation and healing processes re-established normal anatomical structures. Different bone grafting materials are used to correct alveolar bone defects: intra- or extra-oral autologous bone, homologous grafts, heterologous grafts, alloplastic grafts or a combination of the same . Actually a promising material in oral-maxillo-facial surgery is the homologous bone. The homologous graft is available in different forms: Freeze-Dried Bone Allograft (FDBA), Decalcified Freeze-dried Bone Allograft (DFDBA), Fresh bone (FB) and Fresh-Frozen Bone (FFB). Fresh Frozen Bone allograft is collected from the donors from different areas, immediately frozen at –80°C and stored in “bone banks”. Since the bone graft could be collected from different anatomical areas, the aim of this work was to evaluate and compare clinically and hystologically the reconstruction of bone defects using femoral head and iliac crest FFB grafts in oral-maxillo-facial surgery. The allografts were inserted using osteosyntesis devices in 10 patients: 4 patients received femoral head grafts and 6 patients received iliac crest bone allografts. After 6 months the rigid fixations were removed and all patients showed bone regeneration and in the same time were submit to implant surgery. After a clinical evaluation of the bone resorption, the implat site was prepared using a Trephine device to collect alveolar regenerated bone for microscopical analyses. The decalcified specimens were dehydrated in graded alcohol followed by xylene, embedded in paraffin. Seven mm thick section were cut by microtome and stained with haematoxylin-eosin to analise the morphology of bone tissue; with anti-CD34 to evaluate the vascularization and with anti-CD-56 to evaluate osteoblast localization. Femoral head allograft swowed a grater bone resorbtion and bledding that iliac crest allograft bone. In addition a large numer of CD34-positive vessels were found mainly in the uncalcified matrix of both groups of patients. It is notheworthy to observe that due to the absence of cortical bone, vessels appeared more numerous in the patients with femoral head allograft. In addition in both groups we found areas of not calcified matrix with several vessels and osteoblasts. Our findings suggesting that the use of FFB both of femoral head and iliac crest origin is effective in the augmentation of the volume of alveolar ridge. In addition we showed that the biology of bone regeneration is similar using the two type of Fresh Frozen Bone allograft and that the neovascularization of the bone matrix is a key event for bone regeneration. Nevertheless we showed some little differences between femoral head and iliac crest bone due to the absence or presence of cortical bone that could be considered by the surgeon for a more effective surgery and for surgical treatment planning.