Efficacy of Blood and Its Products-boon for Oral Surgeons: Review

A set of scientific researches has focused its attention on discussing the possibility that platelet derivatives are not only coherent for haemostasis, but also have gained popularity in the field of tissue healing. Products obtained from whole blood as a result of centrifugation have wide applications in this field. Various materials are commercially available that are used locally to achieve haemostasis; however platelets and fibrinogen are the natural blood components that exists as a source in coagulation process. Platelets carry platelet-derived growth factors which, when introduced into an injured region, may stimulate a healing response through the recruitment of stem cells, increased vascularization and the production of collagen enhancing both soft and hard tissue healing. Injection of collected venous blood could be a scaffold for new bone formation which is helpful in restricting mouth opening in TMJ subluxation. Injections are inexpensive, simple to acquire, accord minimal trauma with minimal risk for allergic reactions. The purpose of this paper is to provide collective information regarding the various centrifuged products obtained from blood and their application in different ways.


Introduction
The regenerative process in humans by employing autogenous blood is an enhancement in the field of surgery. With-drawl of the whole blood can be maximally utilized once it is centrifuged; to obtain a high concentration of platelets in less amount of plasma for various processes in oral surgery Platelets holds a significant role in healing process. Apart from its well-known role in hemostasis, it also plays its part in regeneration of tissues by releasing of active proteins from the a-granules which results in injury to tissues which in turn releases cytokines and growth factors stimulating the proliferation of cells [1].
Other than this, fibrinogen rich products as a result of centrifugation of whole blood proved to be a useful tool for oral surgeons. It comprises of 0.2% by volume of whole blood, which converts to an insoluble fibrin meshwork in the presence of thrombin [2]. There has always been a demand by surgeons for natural substances that would assist in arrest of bleeding and perfect closure of wound margins. These biologic substances benefits both the surgeon as well as patient by reduction in surgical time, elimination of foreign body reaction, removal of evacuation drains, approximation of flaps with reduced tension, Platelet rich fibrin (PRF): It was developed by Choukroun in 2001 [5] who introduced a new class of platelet concentrates which can be obtained without complex processing and blood handling (Figure 4).
Absence of anticoagulant causes the activation of platelets in the blood sample and thus the coagulation cycle. Thus the conduct should be fast to achieve a clinically usable PRF clot [6] as the chances of failure increases if the duration required to collect blood and launch centrifugation is overly long, failure will occur: The fibrin will polymerize in a diffuse way in the tube and only a small blood clot without consistency will be obtained. Slow fibrin polymerization during PRF processing leads to the intrinsic incorporation of platelet cytokines in the fibrin meshes. They implied that PRF, unlike the other platelet concentrates, would be able to progressively release cytokines during fibrin matrix remodelling [7]. The slow polymerization during PRF preparation seems to generate a fibrin network very similar to the natural one and such a network leads to a more efficient cell migration and proliferation [8]. The PRF serves as a fibrin matrix [9], conducts an important mechanical role by supporting the graft particles as well as promotes cellular migration facilitating,   neo-angiogenesis [10], responsible for the viability of the graft [11][12][13]. It is a simplified, cost effective process which does not require blood handling and usage of anticoagulants. Because of slow polymerization and more potent migration and proliferation of cells, a commendatory healing is obtained with PRF.

Importance of platelet rich centrifuged blood products
1. In response to tissue injury, platelets gets activated resulting in the formation of platelet plug with subsequent hemostasis.
2. Wound healing is initiated by the release of alpha granules in platelets that contains growth factors (Platelet derived growth factor, platelet factor 4, angiopoietins and thrombospondin 1 which promotes proliferation and differentiation at cellular level.
3. 90% of the growth factors are released during the first hour of wound healing followed by gradual and continuous secretion for the remaining 7 days of their viability [14].
4. Growth factors released from platelets also participate in collagen synthesis, providing a scaffold for migration of osteoblasts [15].
5. Quantity of platelets in any wound determines the quality of healing and platelet rich blood products increases that initial number. The PRP and PRF being rich in platelets have an effective use in soft and hard tissue wound healing.

Clinical implications of platelet rich blood products
These products can be used in Soft tissue regeneration or hard tissue regeneration.

Soft tissue regeneration
Skin and mucosal abrasions: All the platelet rich blood products are effectively used for soft tissue regeneration in the field of dentistry. Face being a highly aesthetic zone, the complexities in healing after any intervention poses a great challenge to the surgeon. Scar formation is one of the most undesirable outcomes of the healing process. Early primary closure helps minimizes the scar, but in cases where there is skin loss, it is not always achievable.
Any wound gets covered with a blood clot which is a focal point of initiating healing. A natural blood clot contains 5% of platelets, 95% of red blood cells, <1% of WBC, and large amount of fibrin strands. A PRP clot contains 95% of platelets, 4% of RBC and 1% of WBC. This increased concentration of platelets can be utilized for the purpose of regeneration. PRF is preferred in soft tissue regeneration over PRP as an additional benefit of fibrin membrane that collects platelet concentrate is obtained.
Although cytokines holds an importance, presence of fibrin meshwork of PRF enacts as the determining element responsible for its potential [16]. The PRF membranes assists in wound repair neither by primary intention nor by pure secondary intention, thus termed as modified secondary intention healing [17]. Platelet gels can also be used as a reliable and potent healing tool in the management of skin and mucosal ulcers [18]. Hom et al. [19] performed a study based on the healing efficacy of autologous platelet gel(APG) on fresh skin wounds and concluded that APG not only enhances wound closure but also increases the wound healing velocity.
Periodontal defects regeneration: Platelet rich products display an effective effect in the regeneration of periodontium. Satisfactory results have been obtained by its use in cases of gingival recession and loss of clinical attachment level [20,21]. It has been proposed by Garg et al. [22] that the restorable barrier membrane materials are infused with PRP as degranulation of platelets will take place within 1 week thus the presence of resorbable barrier will restrict epithelial migration.
Platelet rich fibrin is also widely used in root coverage procedures [23] in mandibular anteriors in combination with flaps. It helps in re-establishing the continuity and integrity of the zone of keratinized gingiva and protects the surgical site, promoting soft tissue healing. Jankovic et al. [24] compared the use of PRF with connective tissue grafts in cases of gingival recession and documented better postoperative results in relation to healing and comfort of patient.
Augmentation of facial tissues: Platelet rich products along with the adipose tissues are used for the 3-dimensional augmentation of face. Adipocyte grafts can alone be used for this purpose, but the incorporation of these products to the fat mass allows for improved graft vascularization [25,26].

Hard tissue regeneration
A wide range of bone grafts is available which are in constant use from last few decades. Independent use of blood products or in combination with bone grafts has been reported in various literatures to be a great success in terms of hard tissue regeneration. Various conditions include periodontal intrabony defects [27], mandibular fractures [28]. Extraction sockets [29], maxillary sinus augmentation [30,31], ridge augmentation [32], restoration of mandibular continuity along with autologous iliac crest bone [33], and in treatment of periapical defects [34]. Anand et al. [35] proposed the use of layering the implant surface with PRP as it improves the treatment outcomes in cases where immediate loading is required. PRP when coated on an implant surface forms a surface which bears potential biological activity.
In 2006, Anitua showed that the osseointegration of implants was enhanced by coating the implant surface with PRP prior to insertion into the alveolus [36].
The use of PRP has also been proposed in the treatment of cartilage degeneration of TMJ in early stages of osteoarthritis [37].
Other than these, PRP has been effectively used as an adjunct to the medicinal treatment of various osseous pathologies like osteoporosis, bone metastasis, associated with solid tumors and multiple myeloma, malignant hypercalcemia) where drugs like bisphosphonates(BPs) are indicated however this drug holds a major disadvantage of causing osteonecrosis [38,39]. The incorporation of PRP in such conditions helps in rejuvenation of bone by the help of its growth factors [40].
Platelet gels has also shown successful reconstructive result in the post-resection cases of jaws, alveolar clefts and established fistulas within maxillofacial region [41]. James et al. [13] reported his work on 15 patients who were treated for alveolar ridge and sinus augmentation by using FDBA along with PRP gel formed by autologous thrombin and concluded by histological and radiographic reports that there was sufficient formation of bone around the implants.

Platelet deficient products
Platelet poor plasma-(PPP): The fraction of plasma containing less than 10, 000/μl of platelets is known as platelet poor plasma (PPP) [42]. PPP being rich in fibrinogen is advantageous to use as a sealant for hemostasis.
Fibrin glues-Various commercially prepared adhesives are available that avoids the use of conventional sutures, however, biological glues prepared from the patient's own blood are considered to be the best choice as the risk of contamination is minimized. The same effects can be achieved by Platelet gels and thus can be used alternatively.
Sealants/hemostats: Application of fibrin glue as sealant can be used in patients requiring face-lift for the elimination of wrinkles, rhinoplasty, scar correction, blepharoplasty, and microvascular surgeries for anastomosis as well as in skin grafting. The adhesive nature of the gel permits good flap approximation, haemostasis and. a more accurate closure in comparison to primary closure alone. Being an excellent haemostatic agent it is popular among surgeons as it limits the need of cauterization decreasing the chances of injuring adjacent nerves.

Journal of Universal Surgery ISSN 2254-6758
As autologous fibrin glue imitates the conversion of fibrinogen to fibrin [43], it can be used to arrest haemorrhage in spite of presence of coagulation disorders. While fibrin glues helps to achieve haemostasis and adherence of the flaps [44] autologous platelet gel offers an additional aid of tissue healing, by the presence of high concentrations of growth factors and cytokines in it [45] (Figure 5).
Patients on anticoagulant therapy are at risk of haemorrhage following oral surgical operations and the usefulness of the autologous fibrin glues and platelet gels are useful in order to control haemostasis [46]. As this product prohibits the discontinuation of anticoagulants a few days before the surgical operation, thus reducing the hospital stay and risk of thromboembolism.

Conclusion
Autologous blood products have shown encouraging success in the field of oral surgery by stimulating and promoting healing.