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The science of platelet-rich plasma.

Introduction

Platelet-rich plasma (PRP) is an innovative technological advancement that supports soft- and hard-tissue healing. PRP is an autogenous blood clot containing platelets in high concentration. (1) The use of PRP as an adjunct in various surgeries can help decrease the chance of acquiring a transmissible disease as well as decrease hypersensitivity reactions, since it is acquired from the patient's own blood. PRP contains a vast amount of certain growth factors that improve and increase wound healing through various mechanisms.

Platelet-Rich Plasma

Platelets are remnants of megakaryocytes (bone marrow cells) that live for only about 10 days and can promote natural wound healing. Platelets release several growth factors, such as platelet-derived growth factor, transforming growth factor-B, and vascular endothelial and epithelial growth factors. These factors occur in large concentrations in the PRP and can aid in the replication of osteoid (the initially formed bone matrix), blood vessels, and even collagen. (2)

The use of PRP is not associated with infection at the surgical site because of its acidic ph level, which inhibits bacterial cell growth within the site just like any other acidic solution. No true infection and or complications have been found with the use of PRP as an adjunct to surgery, based on comparisons of bone grafts and skin wounds with the use and without the use of the PRP. (1) Although seen very rarely, the only side effects that the patient may experience result from the collection of the blood, which can cause swelling, bruising, nerve damage, fainting, nausea, or even arterial puncturing at the site of the blood collection area if the blood collection is performed incorrectly. A sterile environment with the use of aseptic technique is necessary when drawing blood for PRP. (1)

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Formation

An aseptic phlebotomy technique is used in the collection of the autologous blood for the preparation of the PRP. The venipuncture site should be completely cleansed with povidone-iodine or alcohol, and then the blood should be drawn using a 19-gauge needle or larger. This will prevent the disruption of the platelets, allowing successful formation of PRP. The test tube into which the blood is drawn should contain anticoagulant citrate dextrose A (ACD-A); this will help bind blood calcium to inhibit the clotting before the PRP is prepared. After the blood has been drawn, various methods of calibrated centrifugation in a special centrifuge will be performed to separate the blood into its basic components and sort them by gradient density. The end result will leave you with packed red blood cells (most dense), PRP (middle layer also called "buffy coat"), and platelet-poor plasma (least dense). Once you have acquired the PRP, a calcium chloride-thrombin solution is added to activate the PRP. This activation will form a gel-like membrane that can then be used in various surgeries. (3)

Benefits

The literature has shown that PRP is beneficial in the healing of various surgical procedures, the most common of which are bone regeneration and soft tissue flaps. Bone needs a constant supply of blood, vitamins and minerals in order to heal adequately.

Statistics show that a natural blood clot contains 95 percent red blood cells, 5 percent platelets, less than 1 percent white blood cells and numerous amounts of fibrin strands. A PRP blood clot contains 4 percent red blood cells, 95 percent platelets and 1 percent white blood cells. (4) Therefore, the use of PRP in bone regeneration initiates a rapid and early cellular response due to the concentration of platelets being used at the site.

During a bone graft, the platelets get trapped in the graft clot. Within a few hours, degranulation of the platelets begins. The degranulation of the platelets produces platelet-derived growth factor (PDGF) and transforming growth factor beta (TGF-B). The PDGF binds to endothelial cells to initiate capillary ingrowths, and TGF-B binds to osteoblasts and stem cells to initiate mitosis and stimulate osteoid production. (5) By day 14 after the placement of the graft, new bone formation is observed. (5)

The amount of platelets in a PRP solution has an average increase of about 338 percent of platelets at the site. Radiographs and computerized tomography (CT) scans, have showed an increase in bone mineral density in PRP-supported grafts that ranged from 1.6 to 2.2 times that of non-PRP-supported grafts, indicating a higher rate of maturity in the bone. (1)

PRP is also very beneficial in the healing of soft tissue, which can be more observable than in bone. For example, if the PRP is used in a skin graft, no signs of erythema will be seen. Microscopically, after six days, a skin graft using PRP shows epithelial budding and mature connective tissue development. After day 45, the site is more flesh colored and indicates wound maturation. The use of PRP for soft tissue healing can help reduce pain and scarring. (1)

Enhancement of osseointegration can also be accomplished through the use of PRP. According to Wilkins, osseointegration is the direct attachment of bone to an alloplastic material. (6) Osseointegration of dental implants results from cell migration, differentiation, bone formation, and bone remodeling along the implant surface; each of these processes is platelet- and blood clot-dependent. (1) The use of PRP can be very beneficial to medically compromised patients with limited bone regeneration, such as patients with diabetes, the elderly, and even patients with osteoporosis. (1)

The PRP coats the site where the implant will be placed, thus subsequently coating the implant surface. The process of osseointegration allows the implant surface, its microgap, and the bony wall of the drill site to connect the bone to the implant surface. This also allows for the degranulation of platelets and their secretion of growth factors that bind to the osteoblast surface membrane to activate a sequence of cell division. (1) As an end result, there will be a greater bone to implant contact, due to the fact that the collagen fibers formed will act similar to "non-breakable steel rods." (1)

PRP can also play an important role in the treatment of third molar sockets by helping prevent alveolar osteitis (dry sockets). This is a very painful bacterial infection that can occur in the third molar area after surgery and promote bone loss there, thus affecting the distal portion of the second molar by creating a pocket or even root caries. A study by Rutkowski et al showed that PRP significantly reduced the incidence of alveolar osteitis by 62.1 percent, from 9.7 percent in patients not receiving PRP to 3.63 percent in patients who received PRP (P=.00043). (3) Although the use of PRP has been proven effective in third molar surgeries, it is not always suggested because of the cost and the amount of time that it takes. Clinicians should always consider who is at risk for alveolar osteitis before dismissing the use of PRP. (3)

The use of PRP can aid in the healing of soft tissue flaps following implant surgeries. Prior to the placement of the implants, the patient has lost bone and blood supply around the area, and scarring of the periosteum can also be seen. The periosteum is a dense connective tissue that contains blood vessels, nerves and osteoblasts (bone-forming cells). (2) Therefore, healing in this area is very important and can easily be compromised. (2)

The use of PRP in soft tissue flaps during the placement of an implant is highly recommended due to the increased risk of infections and scarring of the periosteum. Before the closing of the flap, after the implant has already been placed in the bone, the activated PRP should be placed on top of the bone and implant surface area to prevent any leakage and promote proper seal of the flap.

The Role of the Dental Hygienist

The use of PRP in a dental office can aid in the enhancement of the healing process. Research has proven that the utilization of PRP during certain procedures can decrease swelling, pain and patient discomfort after surgery. PRP is an innovative technological procedure that, when prepared appropriately, can promote an accelerated healing process with no known side effects.

As dental hygienists, we are one of the key elements in maintaining a patient's oral health, but our role is not limited because we have no boundaries in education. The use of PRP is gradually increasing, and our being thoroughly educated about it can contribute to optimal wound healing for our patients. Our commitment to lifelong learning in all aspects of oral care can not only encourage our patients to practice an overall healthy way of life, but also provide essential knowledge to them as they make informed decisions about their own health.

References

(1.) Marx RE, Arun KG. Dental and craniofacial applications of platelet-rich plasma. Chicago: Quintessence Publishing Co.; 2005.

(2.) Tischler M. Platelet rich plasma: utilizing autologous growth factors for dental surgery to enhance bone and soft tissue grafts. N Y State Dent J. 2002; 68(3): 22-4. Available at: www.perfusion.com/cgi-bin/absolutenm/templates/prparticledisplay.asp?articleid=1728&zoneid=5.

(3.) Wilkins EM, Wyche C. Clinical practice of the dental hygienist, 10th ed. Pennsylvania: Lippincott Williams & Wilkins; 2008.

(4.) Bath-Balogh M, Fehrenbach MJ. Illustrated: dental embryology, histology, and anatomy. Pennsylvania: W.B. Saunders Company; 1997.

(5.) Sunitha J, Manjunath K. A combination of platelet rich plasma and hydroxyapatite (osteogen) bone graft in the treatment of intrabony defects--a case report. J Clin Diagnostic Res. 2010; 4(4): 2984-8. Available at jcdr.net/article--fulltext.asp?issn=0973-709x&year=2010&month=A ugust&volume=4&issue=4&page=2984&id=854.

(6.) Rutkowski J, Fennell J, Kern J et al. Inhibition of alveolar osteitis in mandibular tooth extraction sites using platelet-rich plasma. J Oral Implantol, 2007, 33(3): 116-21. Available at: www.miifellows.org/publications/downloads/inhibition_of_AO_with_PRP.pdf.

Martha Macaluso, MLT, RDH, has a passion for dentistry and education. She received her associate degree in Medical Laboratory Technology from Nassau Community College in 2002 and earned her associate degree in dental hygiene at Farmingdale State University where she is currently working on her bachelor's. She won first place for her table clinic presentation, "The Science of Platelet-Rich Plasma," at the Greater Long Island Dental Meeting, and has participated in several table clinics at Greater New York Dental. She currently practices dental hygiene at a periodontal office where she aides in the preparation of PRP. She dedicates this article to the loving memory of her mother, Virginia Freile.

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Title Annotation:clinical feature
Author:Macaluso, Martha
Publication:Access
Article Type:Report
Geographic Code:1USA
Date:May 1, 2011
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