How Do Blood Concentrates Help with Bone and Soft-Tissue Healing?

Ron Zokol, DDS: There have not been many advancements in our past that have enhanced the healing of surgical procedures in both bone and soft tissue as significantly as blood concentrates. The evolution of concentrated blood platelet technology to improve surgical would healing began in the early 1990s with Dr. Robert Marx's use of platelet-rich plasma (PRP). Later, this technology utilizing higher concentrations of viable blood platelets was further developed in the form of platelet-rich fibrin (PRF), which has provided a substantial improvement in both the predictablity and efficiency of wound healing. PRF protocols differ from those of PRP in that the blood is not anticoagulated. Centrifuging to concentrate platelets is common to both, but the development of a natural fibrin matrix in PRF provides a significant difference.

The PRF membrane has a number of characteristics that give it unique and extraordinary value. The physical characteristics of the membrane itself allow it to be stretched 1.8 × with almost perfect elasticity, to be sutured and/or function as a barrier, and to be added to graft materials to enhance vascularization and the provision of growth factors to the healing site.

A significant amount of research has gone into the development of graft membrane materials that would allow a timed release of growth factors to enhance tissue healing over a lengthened period of time. As for PRP, the growth factors are indeed enhanced, but they are released all at once and their effectiveness only lasts hours, not days.

PRF appears to be the answer. Research has shown that some PRF protocols yield products that sustain the release of growth factors for 10 to 14 days. Moreover, this product enhances the healing of any tissue in which it is placed, because it will yield growth factors to influence the progenitor cells of that specific tissue type-similar to the function of platelets anywhere in the body for normal human physiology. The difference is that the platelets in PRF are more concentrated and are released over an extended period of time. Clinical applications include all aspects of bone grafting and soft-tissue grafting/healing.

Bobby Birdi, DMD, MSc:Initially, it is important to understand that any type of autologous blood concentrate is formulated by drawing the patient's blood and then concentrating it through a centrifugation process. This process can involve various tubes and separation techniques, depending on the specific blood concentrate desired. PRP is a concentrate that has been classically used in many areas of medicine. The primary goal of using this or any type of blood concentrate is to provide an increased concentration of growth factors to the area of interest and thus, speed up healing. PRP has been used to aid in soft-tissue wound healing after surgery as well as in a plethora of other applications, such as tendonitis therapy. Generally, PRP is believed to aid in soft-tissue healing, but has little effect on osseous healing due to the fact that the release of its growth factors and their efficacy occurs during a very short period of time (ie, hours).

More recently, we are seeing applications of newer blood concentrates, namely PRF, in dermatology, plastic surgery, sports medicine, and ophthalmology-as well as dentistry. This type of blood concentrate differs tremendously from PRP in that a strong fibrin matrix is formulated through the centrifugation process. This matrix is then commonly pressed into sheets, membranes, and/or plugs that can be used in various procedures, such as dental surgery. Unlike PRP, PRF has been shown to exhibit sustained growth factor release for 10 to 14 days. Furthermore, it provides geometric advantages in the placement and stability of osseous grafts.  Recent evidence has indicated that the use of PRF alone in extraction sockets accelerates osseous healing when compared with the natural healing process of a socket. This is a revolutionary concept. The placement of PRF into dental implant osteotomies prior to implant placement has been shown to benefit dental implant stability values as well. The potential benefits of PRF in accelerated osseous healing look both promising and exciting!

Robert Miller, DDS:Strategies to promote early soft-tissue healing have included platelet therapy in the form of PRP and plasma rich in growth factors (PRGF) and the use of recombinant human platelet-derived growth factor (rhPDGF) and recombinant human fibroblast growth factor (rhFGF). The use of these modalities provides several desired outcomes. First, they facilitate the rapid anastomosis of flap margins to protect bone grafts and implanted devices. Second, they recruit additional cells that promote epithelialization of the site to enhance biotype. And finally, they foster upregulation of fibroblast metabolism, resulting in a more rapid maturation of soft tissue.

Commercially available growth factors, which include rhPDGF and rhFGF, are singular cytokines that address specific pathways for soft-tissue growth. However, other growth factors that contribute to regeneration of the soft-tissue complex are present in low concentrations and may not be available in sufficient quantity to allow rapid maturation of the soft-tissue zone. The use of PRP and PRGF eliminates leucocytes, reducing the availability of critical growth factors. This may result in a delay of soft-tissue healing, even after the early growth of fibroblasts. The sequential steps of early soft-tissue healing include monocyte chemotaxis, fibroblast migration, fibroblast proliferation, angiogenesis, and collagen synthesis. These pathways require the interaction of several cytokines that must be present in the correct ratios to maximize early tissue healing.

Concentrated growth factors and the cells that produce them are now available in the form of leucocyte- and platelet-rich fibrin (L-PRF). Not only are all of the growth factors necessary for early soft-tissue regeneration present in the correct physiologic ratios, they are also concentrated 5 to 10 times. Vital cells that produce these cytokines are trapped within the fibrin mesh, and they continue to release these growth factors for 7 to 14 days. This results in rapid anastomosis of flap margins to protect bone graft sites, increased tissue thickness to enhance soft-tissue biotype, and faster maturation of the dentogingival complex.