PRP to Enhance Pre-Prosthetic Bone Grafts, Dental Implants and Periodontics

/Home/Dental Technology and Research/Stem Cell Research in Dentistry

PRP to Enhance Pre-Prosthetic Bone Grafts, Dental Implants and Periodontics
PRP Central
Although bone augmentation for supporting osseointegrated dental implants has been a routine technique in dentistry for more than a decade, research continues toward improving our ability to manage bone grafts.
Most recently, researchers have focused on the plausability of applying polypeptide growth and differentiation factors (GDFs) to enhance bone regeneration. GDFs are a class of biologic mediators that play a critical role in stimulating and regulating the body's wound healing process. Specific GDFs appear to regulate key cellular processes such as mitogenesis, chemotaxis, differentiation, and metabolismÛall crucial steps in the process of osteogenesis.1 The theory is that applying these growth factors to bone graft material can enhance and even accelerate the normal bone regenerative process.
One strategy for harnessing this benefit is to prepare and apply autologous Platelet Rich Plasma (PRP) to bone graft sites. The PRP is prepared by extracting a small amount of blood from the patient and using a cell separator to sequester and concentrate the platelets.
Platelets are a rich source of at least seven growth factorsÛplatelet-derived growth factors (PDGFaa, PDGFbb and PDGFab) transforming growth factors ?1 and ?2 (TGF-?1 and TGF-?2), vascular endothelial growth factor (VEGF) and epithelial growth factors (EGF).

Marx et al have shown that the cancellous marrow cells present in graft material harbor receptors for these growth factors.4 They also showed radiographically that adding PRP to graft material significantly reduced the time to graft consolidation, maturation, and improved trabecular bone density.4
Components of PRP
Applying PRP to graft material amplifies the influence of PDGF and TGF-?, at least in the initial stages of the bone regeneration process. As the platelets degranulate, these growth factors are released. It is generally agreed that all platelets degranulate within 3 to 5 days and that their initial growth factor activity may expire by 7 to 10 days. This initial boost PRP appears to give the process can be useful nonetheless as it "jumpstarts" the beginning of a cascade of regenerative events that continue to form a mature graft.
PDGF is considered one of the principal healing hormones that appears in any wound, initiating connective tissue healing, including bone regeneration and repair. It is a potent mitogen (triggering an increased number of healing cells), angiogen (generating new capillaries) and an up-regulator of other growth factors (which promote fibroblastic and osteoblastic functions, cellular differention, and accelerated effects on other cells, such as macrophages).2 There is also evidence that PDGF increases the rate of stem cell proliferation.
TGF-?1 and -?2 are involved with general connective tissue repair and bone regeneration. Their most important role appears to be chemotaxis and mitogenesis of osteoblast precursors and the ability to stimulate deposition of collagen matrix for wound healing and bone.6 These growth factors also enhance bone formation by increasing the rate of stem cell proliferation, and they inhibit to some degree osteoclast formation and thus bone resorption.3,7
The fibrin component of PRP also helps to bind the graft material and assists in osteoconduction throughout the graft by acting as a scaffold that supports the new bone growth. PRP also modulates and up-regulates one growth factor's function in the presence of the other growth factors. This feature separates PRP growth factors from recombinant growth factors, which are single growth factors that focus only on a single regeneration pathway.20
Studies of PRP Use
Research focusing specifically on the usefulness of PRP is in its infancy, but thus far, the results appear promising and in agreement with preclincial studies in animals; the first human clinical study showing enhanced bone regeneration when PDGF, TGF-? or other growth factors are applied.9-14 Several orthopedic studies have also shown evidence of beneficial effects from autologous fibrin with a concentration of PDGF and TGF-? contained in it.15-17
In a controlled trial by Marx et al including 88 patients undergoing bone augmentation, two different investigators radiographically assessed the sites treated with graft material plus PRP and the controls treated with graft material only. At 2, 4, and 6 months the grafts with PRP were consistently rated as having reached maturity levels nearly twice their actual levels. Histormorphometry assessment also revealed graft bone densities in the PRP-treated group that were 15% to 30% higher than the controls at 6 months.4
In another controlled study by Anitua of 20 patients who underwent extractions prior to dental implant placement, patients treated with PRP and grafts showed a significantly greater buccolingual/paltal width of bone and epithelialization than controls at 16 weeks. Controls tended to have connective tissue filling the main portion of the defect.18 The author also reported that about 250 other patients had also been treated using PRP with good clinical results.

Conclusion
The use of PRP appears to provide benefits that lead to more rapid and effective bone regeneration. This may be attributed to the concentrated levels of PDGF and TGF-? as well as other growth factors or proteins that have not yet been identified.
This technique does not carry any risk for patients whose blood is used relatively quickly. It also eliminates concerns of disease transmission or immunogenic reaction that exist with allografts of xenografts. Because PRP is prepared at the time of surgery, the possibility of mislabeling a sample is also avoided.
Use of growth factors is particularly attractive for cases with factors that typically reduce the success of bone grafts and osseointegration, including the edentulous, severely atrophic maxilla, patients with osteoporosis, and those with prior dental disease and subsequently scarred and altered tissues.19
Future studies are needed to determine the optimal concentration of the different growth factors and to identify other factors that may exist in PRP which could further explain the benefits of this treatment in wound healing and bone formation.
Some Clinical Applications
Augmentation Grafting of the Maxillary Sinus
Ridge Preservation
Extraction Sockets
Mucogingival Grafts
Marginal Tissue Recession - Root Coverage
Periodontal Defect
Immediate Implant Placement
Third Molar
Failing Implants
Coating Implants and Osteotomy Sites
Particulate and Block Grafts
Biological Membranes and Sealants