Objective: The early effect of platelet-rich plasma (PRP) on bone regeneration in combination with dense biphasic hydroxyl apatite (HA)/beta-tricalcium phosphate (TCP) particles (ratio 60%/40%) was evaluated in rat cranial defects with a diameter of 6.2 mm. We hypothesize that PRP exerts its beneficial effect on bone regeneration within the first and second week after application in a bone defect combined with an osteoconductive material.
Materials and methods: Forty-five rats were used in the study, in which always one cranial defect was created. The defects were filled with HA/beta-TCP particles and HA/beta-TCP particles combined with PRP gel. Some defects were also left unfilled as control. One and two weeks after surgery specimens were retrieved for light microscopy [hematoxylin-eosin, trichrome staining (Masson modification Goldner) and basic fuchsin-methylene blue] and micro-CT analysis to evaluate bone formation and neovascularization. One-way analysis of variance was performed on the raw data obtained from micro-CT analyses.
Results: The histological evaluation showed no effect of PRP on bone formation and neovascularization for both implantation times. In the first week, the defect closure was evaluated subjectively to be between 10% and 50% in all samples, whereas no difference among the groups appeared to occur. After 2 weeks, complete bridging of the original bone defect was observed for most of the empty defects, as well as for the defects that contained HA/beta-TCP particles. The trichrome staining revealed no difference in the number of blood vessels between the PRP and non-PRP groups for both implantation times. The osteoconductive nature of dense HA/beta-TCP particles was confirmed, as the bone formation was guided by their outer surfaces and resulted in a larger amount of newly formed bone in comparison with the empty defects. The quantitative micro-CT analysis demonstrated a statistically significant difference in new bone formation between the empty defects and defects filled with particles after 1 week of implantation, but there was no difference between the non-PRP and PRP groups. In at the second week, no difference in bone formation among all groups was observed, whereas even the non-filled control defects were almost completely closed.
Conclusions: A 6.2 mm cranial defect is not a critical-sized defect in rats. Rat PRP had no effect on the early stages of bone healing in addition to an osteoconductive material. Dense HA/beta-TCP particles showed a beneficial effect on bone formation already after 1 and 2 weeks of implantation in non-critical-sized cranial defects in rats.