Objective: Platelet-rich plasma (PRP) is being used more often in oral implant surgery; however, there have been conflicting results in recent tests of PRP. This study used an animal model with an experimental bone defect to assess the effect of PRP on early-stage bone regeneration.

Methods: Five beagle dogs were studied. The mandibular premolars of each dog were extracted bilaterally, and the area was allowed to heal for 3 months. PRP was prepared using a fully automatic system (Smart PReP^TM, Harvest Technologies Corp., MA, USA). Three bone defects, measuring 3.75 × 7.0 mm (diameter × depth), were prepared on each side of the edentulous areas in each dog. The defects were then filled with PRP, platelet-poor plasma (PPP), or blood clot (control). New bone formation was assessed by histologic and morphometric methods two weeks after surgery.

Results: The average PRP platelet count in this study was 1,034,000 /mm³, and ranged from 825,000 to 1,160,000. Histologically, newly formed bone was seen only near the wall of the bone defect in the controls. A larger area of regenerated bone was seen in the defects that were filled with PPP; however, only woven bone was identified. A large area of regenerated bone, containing a mixture of woven and lamellar bone, was seen in all of the bone defects filled with PRP. Histomorphometrically, there was significantly (ANOVA, Fisher post-hoc test, p < 0.05) more regenerated bone in the defects treated with PRP (28.16 ± 8.55%) as compared with the controls (16.13 ± 7.38%). PPP (20.05 ± 5.61%) did not differ significantly from the controls.

Conclusion: These results suggest that PRP strongly enhances the proliferation and differentiation of osteoblasts in the early stage of bone regeneration.

This study was supported by JSPS Grants-in-Aid for Scientific Research (#14571846).

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