Introduction:

Treating patients suffering from hematological disorders or using anticoagulant medications always presented a main concern. At the beginning fibrin homologous glues were introduced in 1990 by Gibble and Ness in order to face this challenge. (see note 1) Those fibrin glues currently marketed do not contain growth factors and are derivatives of blood components drawn from other donors.

The need for an autologous hemostatic gel provoked the development of platelet-rich plasma gel(PRP gel). Autologous PRP was first introduced to dentistry by Marx et al. in order to improve bone healing. (see note 2) PRP is a product that contains elevated levels of autologous growth factors. These growth factors are maintained in the same ratios as in peripheral blood.

Platelet Rich Plasma (PRP) is composed of platelets, lymphocytes and plasma. Platelets are cells that are partially responsible for causing blood to clot. Platelets are a small disk or plate like structure. They are non-nucleated blood elements with very fragile membranes. Platelets adhere to uneven or damaged surfaces. The average human platelet count is 250,000/mm3. Platelets are formed in the red bone marrow by the fragmentation of megakaryocytes. Platelets contain large amount of natural growth factors. The platelet count in PRP can exceed 1 million platelets per micro liter.

Platelet degranulation is a physiologic process which proceeds upon contact with damaged vascular endothelium, collagen and other biochemical mediators. Physical damage to the platelet itself is to be avoided in order to preserve physiologic function, i.e., degranulation within the wound and not within the collection system. In theory, this would allow for the delivery of the greatest concentration of actual growth factors to the wound. PRP is more likely a concept of amplifying a biological event that is happening any how in an injured tissue.

Growth factors (more then 30 identified in platelets) shown to enhance the body's natural healing process include:

There are also others products available, such as recombinant synthetic growth factors: these products are usually synthetic derivatives of a single growth factor. Signals generated from PRP-derived growth factors reach local pluripotent, mesenchymal and epithelial cells and enhance their local migration, division and matrix synthesis. As a result, PRP has been suggested to increase the early rate of bone deposition and its quality during guided bone regeneration procedures. (see note 4)

Processing stage:

As described by most authors, coagulation of the PRP to form a gel is acquired by mixing 6 ml of PRP with 1 ml of calcium thrombin (10% calcium chloride + 1000 units thrombin/ml):

As observed by some authors, PRP is meanful when acting on living cells- osteoblasts, osteoclasts, and fibroblasts. It has no meaning when used only with bovine bone, or banked bone alone.

Case presentations:

Case 1: Sinus lift

Patient presented with second and third hopeless molars. after extraction, socket preservation and sinus lift were preformed using DFDB + autogenous bone + PRP.		5 Months later, dense D1 type bone can be noticed in the augmented sites.		3 screwvent implants were placed (4 months after placement)
At 1 year check-up after rehabilitation.		3 years follow up clinical appearance		X-ray at 3 years follow up.

Case 2: vertical bone augmentation

Hopeless roots to be extracted				After extraction
PRP coagulum: autologus bone+ bovine bone+ PRP		PRP coagulum covered with titanium reinforced membrane		After suturing
8 days suture removed		5 months later- membrane removed and implant placement		Bone height gained
Panoramic before rehabilitation
		Clinical and x- ray after PFM bridge screw retained delivered