The purpose of this study is to analyze histomorphometrically, and also through immunohistochemical reactions, the influence of platelet-rich plasma (PRP) or platelet-rich fibrin (PRF) on bone healing in surgically created critical-size defects (CSD) in rats. 90 rats will be divided into 3 groups: Group C (control), Group PRP (platelet-rich plasma) and Group PRF (platelet-rich fibrin). A 5 mm diameter CSD will be created in the calvarium of each animal. In Group C, the defect will be filled with blood clot only. In Group PRP and Group PRF, the defects will be filled with PRP and PRF, respectively. All groups will be divided into subgroups (n=10) for euthanasia at 07, 15 or 30 days postoperatively. The area of the original surgical defect and the surrounding tissues will be removed en bloc. The specimes will be processed and embedded in paraffin. Serial sections 6 µm-thick will be cut in a longitudinal direction to the sagittal suture. Some sections will be stained with hematoxylin and eosin for histomorphometric analysis. The amount of new bone formation will be calculated as a percentage of the total area of the original defect. Proliferating cell nuclear antigen (PCNA), runt-related transcription factor - 2 (RUNX-2), bone alkaline phosphatase (BALP) and bone morphogenetic protein - 2 (BMP-2) immunohistochemical staining will be performed. The results will be analyzed by light microscopy. The data will be submitted to statistical analysis.
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