Applications of PRP in Oral and Maxillofacial Surgery

Enhancement of Autogenous Bone Grafts

PRP added to autogenous cancellous marrow graft

PRP was first described for use and has documented efficacy in accelerating autogenous bone graft healing. It has been shown to improve the rate of bone formation by 1.62 to 2.18 times that of controls. It also increases the density of the bone formed by 19% – 25% when measured at four months and six months.

Continuity Grafts:

In the context of continuity defects these grafts are accomplished in an operating room setting. The PRP should be developed prior to the infusion of large fluid volumes which will dilute blood components and prior to any significant tissue wounding which will sequester platelets in the wound. The PRP may remain on the sterile field in an anticoagulated state for up to 8 hours. However, once “activated” with calcium and a clot initiator, it should be directly used.

Normal bone density radiographically observed in graft without PRP at 4 months

Increased bone density raiographically observed with PRP enhanced graft at 4 months

The nature of large continuity grafts recommends incorporating the PRP into the graft during placement with a layering technique. That is, small amounts of PRP gel are added to the graft as it is placed. It is then best to place some on the graft surface. About 20 cc’s to 35 cc’s of PRP are usually required depending on the size of the graft.

Sinus Lift Grafts:

Sinus lift grafts of autogenous bone will require about 5 cc’s of PRP per sinus lift. In this instance, adding the PRP to the cancellous marrow graft in a beaker and initiating clotting will gel the particulate nature of these grafts together. It will allow for a direct handling and placement into the prepared sinus lift. In a similar manner, PRP may be added to mixtures of autogenous bone and “bone graft expanders” such as the numerous “bone substitute” products which are available. However, as has been shown in sinus lift grafting, a minimum of 20% of this composite graft must be autogenous bone. Since PRP acts upon osteoprogenitor cells and mesenchymal stem cells it will enhance the bone formation from the autogenous component. As of the time of this writing there is no proof of PRP’s beneficial effects on “bone substitute” use.

Ridge Augmentation Grafts:

Both vertical and horizontal ridge augmentation procedures will benefit from PRP. If either a cortical-cancellous block or a strictly cancellous marrow graft is used the PRP is incorporated into and on the surface of the graft. This will usually require about 5 cc’s of PRP. If possible, a PRP membrane over this type of graft is useful. As an alternative, adding PRP to the membrane material may also be accomplished.

Peri-Implant Grafting:

When implants are placed into tooth sockets, a gap between the implant surface and the lamina dura often exists. PRP placement into this area will act as a platelet and fibrin enriched blood clot promoting the natural osteoinduction of tooth socket healing.

When implants are placed into thin edentulous areas there is often a portion of the implant surface without bone coverage. In these areas small autogenous bone grafts obtained from such places as the chin, tuberosity, ramus, adjacent edentulous areas, or trephined from an implant placement area are recommended. PRP use within these small grafts together with a three month or longer resorbable membrane provides an early result of complete bone coverage for the implant.

Split thickness skin graft donor sites at one week. PRP advanced healing on the right evident as compared to control on left

Split Thickness Skin Graft Donor Sites:

The value of PRP in soft tissue healing enhancement is just now emerging. It has already demonstrated efficacy in the healing of split thickness skin graft (STSG) donor sites. In this instance a PRP gel is developed and placed on the donor site surface and retained with an occlusive dressing such as Opsite® or Tegaderm®. When this dressing is removed (seven days) the donor site will have significant epithelialization. A PRP treated STSG donor site will be advanced to about a three week maturity at one week. The revascularization is quickly enhanced by the angiogenic activity of PDGF and TGFß. The fibrin acts as a scaffold for the epithelial migration. Together they promote a sufficiently rapid granulation tissue development and epithelializaiton so that individual patients are spared the prolonged crusting phase in STSG donor site healing. They therefore have reported less pain and an earlier return to normal activity.

Autogenous whole blood inserted into centrifuge bag of PCCS office device

PCCS office device is one of several office devices capable of producing a concentration of platelets for the clinician to develop clinically useful PRP

Red blood cell button, “buffy line” (PRP) and plasma. Resuspension of these components generates clinical PRP

PRP developed from PCCS office device

PRP suspended platelet concentrate withdrawn into syringe for clinical use

Development of Platelet Rich Plasma

Platelet Rich Plasma (PRP) is processed from autologous blood using various forms of centrifugation and cell separation principles. Essentially whole blood is anticoagulated with citrate and is centrifuged into its three basic components by gradient density. These components are: red blood cells (most dense) the “buffy coat” which is the Platelet Rich Plasma as a middle component, and Platelet Poor Plasma (PPP) as the least dense.

Operating Room Devices:

When operating room devices are used for major surgery 400 ml of blood is used, which will yield about 40 ml of PRP. The remaining red blood cell volume (160 ml) and the remaining PPP volume (200 ml) are returned to the patient. The PRP is stable with this sterile processing technique for up to eight hours at room temperature. To develop a platelet gel from PRP for clinical use, 7 ml of the PRP is drawn into a 10 ml syringe, ¼ ml of the “activator” is then drawn into the same syringe along with 1 ml of air to act as a mixing bubble. The mixture will clot “gel” within six seconds and should be used immediately. The “activator” is a simple mixture of 10 ml of 10% CaCl₂ and 5,000 units of topical bovine thrombin. The CaCl₂ will neutralize the anticoagulant effect of the citrate and the bovine thrombin will initiate the clotting cascade. Although bovine thrombin has been proven to be completely safe in PRP use, some clinicians and countries have a reluctance to use bovine products. Platelet Rich Plasma can still be activated by using 1 ml of autologous whole blood and a small amount of autogenous cancellous bone, both of which contain human thrombin.

Office Devices:

To serve the numerous needs of clinical office procedures related to oral and maxillofacial surgery and dental implant practice, several office devices are now available. These devices utilize only 45 ml to 110 ml of autologous whole blood in a closed sterile system. These devices will yield 6 ml. to 12 ml of PRP discarding the unused blood. Therefore re-infusion is unnecessary and is actually contraindicated in the office setting. These devices are easy to use and yield PRP with platelet counts five times that of the baseline peripheral blood. With each office device the specific protocol may vary somewhat. However, each will draw the prescribed amount of autologous whole blood into a 60 ml syringe containing 5 ml of citrate. The anticoagulated blood is then placed into the office device for processing, which will take approximately 20 to 25 minutes. The final PRP product is separated from the red blood cells and PPP into a syringe. The red blood cells and PPP are then discarded. Each office device will yield sufficient PRP for most all office procedures. Roughly 1 ml of PRP can be obtained for every 10 ml of whole blood drawn.

The usual office logistics are for procedures accomplished under intravenous sedation techniques. The clinician will accomplish the venipuncture and draw the prescribed amount of whole blood with the citrate added to the syringe. The same catheter is then used to initiate the intravenous sedation. Trained nurses or trained office personnel will develop the PRP while the clinician begins the actual surgery. In this manner, PRP development does not interfere with or detract from the surgical procedure.

Platelet Rich Plasma Constructs

PRP added to Graft:

Platelet Rich Plasma is most commonly applied directly into an autogenous bone graft. Its gel consistency will improve the handling properties of the particulate cancellous marrow. In this manner, the PRP gel is evenly distributed throughout the graft.

Another alternative is to place the cancellous marrow graft in increments adding “activated” PRP to each increment and then a final application on top of the graft.

Commercial membrane impregnated with PRP and autogenous graft with PRP

PRP Membranes:

The activated PRP gel may be made into a bio-resorbable membrane which will last for approximately five to seven days. This is accomplished by “activating” the PRP into a gel and placing 3 ml to 4 ml on a smooth surface. After approximately five minutes the PRP gel can be taken off the surface as a membrane. This membrane will consist of fibrin, in which is enmeshed the platelets. It may be used over sinus lift windows, to cover sinus membrane perforations, or over dental implant fixtures.

PRP Added to Commercial Membranes:

Commercial Membranes such as Collatape®, Resolute®, or Osseoquest®, have a texture which will absorb the “activated” PRP gel. This will allow the clinician to apply growth factors to longer lasting membranes so as to gain the benefit of each.