The biology of platelet-rich plasma

Maxillary sinus floor augmentation using autogenous bone grafts and platelet-enriched fibrin glue with simultaneous implant placement

OBJECTIVE

The aim of this study was to evaluate the use of autogenous bone in combination with platelet-enriched fibrin glue as a grafting material for maxillary sinus augmentation with simultaneous implant placement in dogs.

STUDY DESIGN

The mucous membranes of 12 sinuses in 6 dogs were elevated bilaterally. In the right sinus, autogenous bone mixed with platelet-enriched fibrin glue was grafted into the space between the membrane and the sinus wall. In the left sinus, autogenous bone alone was grafted as a control. At the same time, 2 dental implants were inserted into the grafting material through the maxillary sinus floor. The animals were killed 6 months after surgery.

RESULTS

The mean bone-implant contact was 40.5% on the fibrin glue side and 32.3% on the control side (P < .05). The mean height of newly formed bone in the augmented area was 12.2 mm on the fibrin glue side and 10.7 mm on the control side (P < .05).

CONCLUSION

The results indicate that the use of autogenous bone mixed with platelet-enriched fibrin glue can achieve results superior to those for grafts of autogenous bone alone. The specific improvements of this technique include enhanced osseointegration of dental implants and increased height of new bone.

Platelet-Rich Plasma in Endoscopic Sinus Surgery

The author designed a study to assess the healing properties of platelet-rich plasma (PRP) after endoscopic sinus surgery in 30 patients with bilateral and symmetrical chronic rhino sinusitis that was refractory to medical management. At the conclusion of each operation, PRP was introduced into the middle meatus of a randomly chosen side, while the other side was treated normally and served as a control. Patients were followed until both sides healed. After 13 operations, follow-up evaluations demonstrated no benefit to the use of PRP, and the study was terminated early. In general, both sides healed quickly and uneventfully as expected. There appears to be no advantage to the use of PRP in endoscopic sinus surgery.

The bone regenerative effect of platelet-rich plasma in combination with an osteoconductive material in rat cranial defects

The effect of platelet-rich plasma (PRP) on bone regeneration, in combination with an osteoconductive material, was evaluated in a rat model. Cranial defects, 6.2 mm in diameter, were filled with HA/beta-TCP particles, HA/beta-TCP particles combined with PRP and HA/beta-TCP particles combined with PRP gel, where some were left empty as a control. After 4 weeks of implantation histological, histomorphometrical and micro-computed tomography analyses revealed no difference in new bone formation among the groups. Further, no additional effect of PRP gel in comparison with PRP liquid was detected, except for the increased handling capacity of the graft. These findings suggest that PRP had no positive effect on bone formation in addition to an osteoconductive material after an implantation period of 4 weeks. Also, no negative effect was seen, and neither PRP nor HA/beta-TCP hampered bone ingrowth into the defects.

The Role of Platelet-Rich Plasma in Sinus Augmentation: A Critical Review

Although the lateral wall sinus lift is a predictable clinical procedure to increase vertical bone height resulting in implant success rates comparable to that of native bone, the issue of extended healing periods remains troublesome. Clinicians and researchers have investigated several methods, including addition of growth factors and peptides, to reduce this healing time and enhance bone formation within the subantral environment. Platelet-rich plasma (PRP) is an autologous blood product containing high concentrations of several growth factors and adhesive glycoproteins. The incorporation of PRP into the sinus graft has been proposed as a method to shorten healing time, enhance wound healing, and improve bone quality. This article reviewed pertinent literature assessing the effect of PRP on sinus augmentation. Currently, the literature is conflicting with respect to the adjunctive use of PRP in sinus augmentation. Factors that may contribute to this variability include variable/inappropriate study design, underpowered studies, differing platelet yields, and differing graft materials used. In addition, methods of quantifying bone regeneration and wound healing differ between studies. At present, because of limited scientific evidence, the adjunctive use of PRP in sinus augmentation cannot be recommended. Further prospective clinical trials are urgently needed.

Platelet releasate increases the proliferation and migration of bone marrow-derived cells cultured under osteogenic conditions

Concentrated platelets and their products are currently being used as a clinical tool to accelerate endosseous wound healing. However, there is little understanding regarding the actions of platelets and platelet-released products on osteogenic cells. We show, herein, that releasate from thrombin-activated platelets increases the migration and proliferation of osteogenic cultures of bone marrow cells. Using a scratch wound assay, we demonstrated that platelet releasate (PR) stimulated up to a 2.4 +/- 0.5-fold increase in wound closure in serum-free medium, relative to a control containing thrombin. In the presence of serum, the addition of PR resulted in a 1.45 +/- 0.13-fold increase in scratch closure. To isolate cell migration from the effects of cell proliferation, cell monolayers were pre-incubated with 5, 10 and 20 microg/ml of Mitomycin C (MMC), which is a potent inhibitor of cell proliferation. This resulted in a large decrease in the leading front of scratch closure, which indicates that PR stimulated cell mitogenesis. However, irrespective of MMC pre-treatment, PR stimulated a motogenic response. These results provide evidence of possible mechanisms by which platelets could influence bone regeneration.

The effect of platelet-rich plasma on the cellular response of rat bone marrow cells in vitro

The aim of this study was to investigate the effect of platelet-rich plasma (PRP) on the proliferation and the differentiation of rat bone marrow cells (RBMCs). PRP, platelet-poor plasma (PPP), and bone marrow cells were derived from the rats (hearts and tibia) and the cells were cultured with or without PRP or PPP (0 [control]), 0.2 approximately 10 microL/mL). The proliferation of RBMCs was measured on days 2 and 4, and alkaline phosphatase (ALP) staining and activity measurement were evaluated to determine the effect of PRP on the differentiation on days 4 and 8. PRP enhanced the proliferation significantly compared to the control group (P < .05). These enhancements were greater than ones induced by the addition of PPP. ALP staining appeared to show that PRP decreased the number of ALP positive cells and ALP activity significantly (P < .05). Our results demonstrate that PRP stimulates the proliferation but suppresses the differentiation of RBMCs.

Influence of Platelet-Rich Plasma Added to Xenogeneic Bone Grafts in Periimplant Defects: A Vital Fluorescence Study in Dogs

BACKGROUND

The use of platelet-rich plasma (PRP) has been suggested in order to increase the rate of bone deposition when sites are augmented prior to or in conjunction with dental implant placement.

PURPOSE

The goal of this study was to investigate whether the addition of PRP to xenogeneic bone grafts would increase the rate of bone formation in dogs.

MATERIALS AND METHODS

Ninety endosseous dental implants were inserted in the mandibles of nine hound dogs. Subsequently, mesial and distal three-wall periimplant defects were surgically created. Defects were randomly assigned to three groups: demineralized freeze-dried bone graft plus platelet-rich plasma (DFDBG plus PRP), demineralized freeze-dried bone graft alone (DFDBG), and no treatment. Postsurgically each dog received a series of three fluorescent labels for estimation of bone cell activity at baseline and during different stages of healing, with particular attention to the bone formation rate per tissue volume (BFR/TV). Animals were sacrificed at 1 month, 2 months, and 3 months, and specimens were subjected to analysis by fluorescence microscopy. Treatment effects were evaluated with analysis of variance models.

RESULTS

Overall, the average BFR/TV differed by treatment although this difference approached only minimal statistical significance (p = .057). The largest difference occurred between periimplant defects treated with DFDBG only and defects that were not treated (mean percentage BFR/TV, 0.0720% vs 0.0994%). There was no evidence of an overall treatment effect (p = .27) for the mineral apposition rate (MAR) values. The data also suggest a consistent variability in the bone formation parameters among the three groups at different healing points.

CONCLUSION

In this animal model the addition of PRP to xenogeneic bone grafts did not demonstrate evidence of faster bone formation during healing. However, limitations of the histologic technique possibly played a negative role in the assessment of bone formation parameters.

Sinus floor augmentation with simultaneous placement of dental implants in the presence of platelet-rich plasma or recombinant human bone morphogenetic protein-7

The aim of the present study was to evaluate the possible benefit of platelet-rich plasma (PRP) in sinus grafting as compared with recombinant human bone morphogenetic protein-7 (rhBMP-7). For this purpose, we performed a bilateral sinus augmentation with anorganic bovine bone and simultaneous insertion of a titanium screw implant in five miniature pigs. Six hundred microliters of PRP and 15%-vol. autologous bone, which was collected with a trap during preparation of the implant recipient site, were added to the right sinus and 420 microl rhBMP-7 to the left sinus. A polychrome sequential labeling was performed. The animals were sacrificed 6 weeks after surgery. Undecalcified ground sections were evaluated by microradiography, digitized histomorphometry and under fluorescent light. The mean bone-implant contact using rhBMP-7 was 45.8% and 5.7% under PRP (P=0.002). The mean height of newly mineralized bone in the augmented area using rhBMP-7 amounted to 8.3 mm as opposed to 3.6 mm under PRP (P=0.013). Using PRP, the mean area of the newly formed bone was enhanced (51.3%) as compared with rhBMP-7 (33.1%); however, this difference was not statistically significant (P=0.081). In conclusion, under the selected experimental conditions the use of rhBMP-7 led to superior outcomes with regard to the osseointegration of dental implants and the height of new bone as compared with the use of PRP.

Efficacy of platelet-rich plasma in alveolar bone grafting

PURPOSE

In this study, we performed alveolar bone grafting with autologous iliac cancellous bone incorporation with platelet-rich plasma (PRP) and evaluated its efficacy in osteoregeneration.

MATERIALS AND METHODS

Seven alveolar cleft patients with adult dentition (average age, 16.1 years) underwent iliac bone grafting with PRP. Quantitative evaluation of regenerated bone was made with 3-dimensional computed tomography scans and compared with controls.

RESULTS

The average of the volume ratio of regenerated bone to alveolar cleft in cases with PRP was higher than in controls (P <.05). There were no complications from the blood draw or PRP.

CONCLUSION

PRP was a safe and cost-effective source for growth factors and was easy to extract. It could enhance the osteogenesis of alveolar bone grafting in cleft lip and palate patients and may useful for subsequent orthodontic therapy.

Effect of platelet-rich plasma on bone regeneration in autogenous bone graft

In this study, we evaluated the effect of platelet-rich plasma (PRP) on bone regeneration in an autogenous bone graft in a canine model. The mandibular premolar teeth had been bilaterally extracted previously, and the ridges had been allowed to heal for 3 months. After this period, continuity resection was performed on both sides of the mandible. One defect (the PRP group) was reconstructed with the original particulate bone mixed with PRP. As a control, the contralateral defect (non-PRP group) was reconstructed with the original particulate bone alone. Biopsies after 6 weeks showed lower levels of bone formation in the PRP group than in the non-PRP group, and fluorescence microscopy revealed a delay in the remodelling of grafts loaded with PRP. These findings suggest that the addition of PRP does not appear to enhance new bone formation in autogenous bone grafts.

Influence of PRP on autogenous sinus grafts. An experimental study on sheep

Since platelet -rich plasma (PRP) has been introduced to the field of oral surgery, it has become a widely accepted additive for bone regeneration treatment. The aim of this study was to evaluate the regenerative capacity of PRP in a sinus graft study on sheep. Twelve adult sheep underwent a bilateral sinus floor elevation procedure with cancellous bone from the iliac crest. Unilaterally, PRP was administrated to the bone graft. After 4 (six sheep) and 12 weeks (six sheep), bone biopsies were obtained from each site. With histomorphometric analysis we evaluated both the percentage of newly formed bone within the grafted site and the percentage of the contact area between the grafted bone and the newly formed bone. After 4 weeks the mean proportion of newly formed bone on the control side was 26.1%, whereas it was 29.2% on the test side. After 12 weeks it was 46.9% on the control side and 51.1% on the test side. The area of contact between the graft and the newly formed bone was 73.0% on the control side and 78.5% on the test side after 4 weeks, and 87.2% on the control side and 90.1% on the test side after 12 weeks. A statistical analysis did not reveal significant differences between the control and the test side. The results of the present experimental study show a regenerative capacity of PRP of quite low potency. Further basic research is needed to investigate more profoundly the possibilities of PRP in bone regeneration.

Sinus grafting with autogenous platelet-rich plasma and bovine hydroxyapatite. A histomorphometric study in minipigs

In this study, bovine hydroxyapatite (HA) alone or in combination with activated platelet-rich plasma (PRP) was examined for its usefulness for single-stage sinus grafting in minipigs. In 12 adult minipigs, Schneider's membrane of 24 sinuses was elevated bilaterally through an extra-oral approach. The material was divided into two groups of 12 sinuses. In one of these groups, the space between Schneider's membrane and the sinus wall was grafted with activated autogenous PRP and HA (PRP side). In the other, HA alone was used for grafting (control side). At the same time two dental implants with a machined surface were inserted into the grafting material through the facial sinus wall. Four animals of each group were sacrificed at 3, 6 and 12 weeks, and undecalcified thin-cut and ground sections (Donath 1988) stained with toluidine blue were prepared. In the facial sinus wall, fewer bone-to-implant contacts were present on the PRP side at 3 and 6 weeks than on the control side. At 12 weeks, the PRP side had caught up with the control side. In grafted bone, contacts on the PRP side were more extensive than on the control side at 3 weeks, had dropped below control side levels at 6 weeks and surpassed these at 12 weeks. This study showed that PRP has a differential effect on osseointegration in grafted bone and local host bone. Combined with HA it was not demonstrably superior to HA alone.