Effects of Platelet-Rich Plasma at the Cellular Level on Healing of Autologous Bone-Grafted Mandibular Defects in Dogs

Abstract

This study describes the effect of platelet-rich plasma (PRP) at the cellular level on immediate autologous bone grafts in dog mandibles. Twelve adult dogs weighing 40 to 50 pounds received bilateral inferior mandibular border resections measuring 2 cm x 1 cm. The right side was grafted with milled autologous iliac corticocancellous bone along with 2 cc of PRP taken from the same animal. The left side had the same amount of milled bone placed in the defect without PRP. Three animals were sacrificed at 1, 2, 3, and 6 months postsurgery. Ten and 3 days before sacrifice, all dogs received 10 mg/kg body weight of intravenous tetracycline. At sacrifice, the grafts along with adjacent native bone were harvested and immediately fixed in Carson's fixative for 48 to 72 hours. The samples were then dehydrated over a 2-week period in a graded ethanol series and embedded in Spurr's plastic. Two 100-micron sections from the center of each graft were cut, mounted on glass slides, ground to 40 microns, and stained. A digitally generated grid was superimposed over each section, to give 32 fields of 2.5 mm2. Each of these fields was examined at a magnification of x100 to determine the number of osteoblasts and osteoclasts present. The mean average of the total numbers of osteoblasts and osteoclasts were significantly higher in the PRP graft sites than in the non-PRP graft sites at 1 month. However, if specific fields were compared, then 14 of the 32 fields showed no difference in the number of osteoblasts and osteoclasts. At 2, 3, and 6 months, there was no significant difference in the total number of osteoblasts or osteoclasts in the PRP and non-PRP grafts, or in any of the 32 fields. At the cellular level, PRP increased the number of osteoblasts and osteoclasts recruited to the graft site at 1 month, and this overall increase was more evident at the superior and lateral margins of the graft than in other areas. Fields along the inferior margin showed the fewest number of cells for both the PRP and non-PRP grafts. At later times there was no significant difference in the number of osteoblasts and osteoclasts in the PRP and non-PRP graft sites in any region of the grafts. This study indicates that the increased number of osteoblasts and osteoclasts in the graft sites due to the addition of PRP was short-lived, and that autologous bone grafts without PRP had similar numbers of active bone cells after 1 month in this animal model.