Bone tissue engineering offers a potential alternative to conventional grafting by combining biocompatible scaffolds with biological stimulants. Polycaprolactone (PCL) is a biodegradable polyester with good mechanical strength and biocompatibility. Hydroxyapatite (HA) is a calcium phosphate mineral that is a major component of bone and has excellent bioactivity and biocompatibility. This research investigated the histopathological effects of PCL-HA nanocomposite scaffolds along with their combination with platelet-rich fibrin (PRF), on the regeneration of bone in rabbit calvarial bone defects. Four circular full-thickness bone defects of 5.00 mm in diameter were created on the calvarial bone of 15 male New Zealand white rabbits. Three defects were filled with PRF, PCL-HA, and PCL-HA/PRF, and one defect was served as a control with no filler. Histopathological evaluations were conducted at 4-, 8-, and 12-weeks post-implantation. Data were evaluated using the Kruskal-Wallis and Mann-Whitney U tests. Significant differences were observed between the treatment and control groups regarding bone regeneration throughout all 12th weeks studied. In the 4th weeks, no significant differences in bone regeneration were noted among the treatment groups. In the 8th weeks, most new bone formation was observed in the PCL-HA/PRF group. Both the PCL-HA and PCL-HA/PRF groups significantly improved bone regeneration compared to the control and PRF groups, with the PCL-HA/PRF group demonstrating the greatest bone formation, and vascularization and the lowest inflammation by the 12th week. Thus, PCL-HA/PRF could be considered as a suitable alternative to bone grafts and could be increasingly utilized in orthopedic surgery and bone tissue engineering.

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