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Objectives: The aim of the study was to evaluate, by morphological and immunohistochemical analyses, the in vivo bone regeneration obtained through a resorbable equine-derived particulate biomaterial, and to compare it with autologous bone from calvaria used for the same purpose. Methods: Patients needing pre-prosthetic rehabilitation of the posterior maxilla were treated with sinus lifting using an equine-derived particulate biomaterial (Group 1) or with onlay graft plus sinus lifting through autologous bone of the calvaria (Group 2), according to the severity and the morphology of the bone defect. Bone specimens were withdrawn from regenerated sites six months after grafting; the behavior of the different grafts was tested by histological and immunohistochemical analysis, with attention to the OPG/RANKL ratio and to the expression of proteins involved in the graft integration process, such as TGFβ1, VEGF, BSP, and SPARC. Results: Morphological analysis reveals remnant granules of biomaterial in Group 1 in parallel to a good integration between autologous bone graft and host tissue. TGFβ1 expression does not show any significant difference in the two groups. OPG/RANKL ratio and VEGF expression appear higher in Group 1, while the expression of BSP and SPARC is higher in Group 2. Conclusions: Our results show that both grafts have a close integration with the host tissue, associated with a comparable clinical performance. However, at the same experimental time, autologous graft triggers a more intense regenerative process, driven by the OPG/RANKL/RANK intracellular signaling system, and an active phase of bone remodeling, as showed by elevated BSP and SPARC expression, probably ensuring a better primary stability of the implant and a high predictability of implant-prosthetic rehabilitation

Autologous bone is considered the gold standard for bone regeneration, even if different heterologous bone substitutes have been proposed to overcome the limits related to its use. The aim of this study was to analyze and to compare the molecular events switched on by autologous or heterologous bone graft insertion, focusing on TGFβ1 expression and OPG/RANKL ratio, to analyze resorption process, and estimating graft vascularization, new bone tissue deposition and its mineralization, through VEGF, BSP and SPARC expression evaluation, respectively. Patients needing pre-prosthetic rehabilitation of the posterior maxilla were treated using an equine-derived biomaterial (Group 1) or calvaria autologous bone (Group 2), according to the morphology of the bone defect. Bone graft integration was evaluated on bone samples obtained from the treated areas at the moment of dental implant insertion, by morphological and immunohistochemical analyses for TGFβ1, OPG, RANKL, VEGF, BSP, and SPARC expression. Morphological analysis shows the presence of biomaterial residual granules in Group 1, in parallel to a good integration between graft and host tissue. Moderate TGFβ1 expression is seen in both Group 1 and Group 2. OPG/RANKL ratio appear higher in Group 1; VEGF expression appears very strong in Group 1 and strong in Group 2, while BSP and SPARC expression results weak in Group 1 and moderate in Group 2. Results reveal the good integration between both types of graft and the host tissue, even though autologous graft seems to produce a faster regenerative process, as evidenced by the different expression of the investigated molecules. According to these observations, the clinical use of heterologous particulate equine-derived biomaterial may ensure long-term predictability of implant-prosthetic rehabilitation, comparable to that obtained with autologous bone graft.