Treatment of Periapical Lesions using a Combination of Bone Graft and Platelet-rich Fibrin

INTRODUCTION

The success of endodontic therapy depends on complete periapical repair and regeneration. In a majority of cases teeth with periapical lesions heal satisfactorily after nonsurgical endodontic intervention. However, there are cases with persisting symptoms and infection that require periradicular surgery in order to remove the pathological tissues and to eliminate the source of irritation, and promote healing. Abramovitz et al. (2002) have reported that treatment of 24.5% of the cases was impossible without surgical therapy¹. Periradicular surgery has become an established treatment option in endodontic surgery.² Surgery may be undertaken after unsuccessful retreatment, or when retreatment is impossible or has an unfavorable prognosis.³

The regeneration of bone following periapical surgery can be facilitated by placing bone graft into the periapical defect. Numerous therapeutic grafting modalities for restoring osseous defects have been investigated. These include autografts, allografts, xenografts and alloplasts. The selection of the material is governed by its biologic acceptability, predictability, clinical feasibility, patient acceptance as well as minimal operative hazards and postoperative sequelae. However, it is difficult to find a material with all these characteristics. Several calcium phosphate biomaterials have been tested since the 1970s and are currently available for clinical use. They have excellent tissue compatibility and do not elicit any inflammation or foreign body response. These materials are osteoconductive, meaning that the matrix of the graft forms a scaffold that favours outside cells to penetrate the graft and form new bone^3,4. In this case report, synthetic tricalcium phosphate (TCP) and calcium hydroxyapatite granules were used as a bone graft in the periapical lesions.

However, the key to tissue regeneration is to stimulate a cascade of healing events that, if coordinated, can result in the completion of integrated tissue formation. This is possible only with the use of growth factors, extracellular matrix and the use of bone morphogenetic proteins instead of routinely used synthetic bone grafts, as they induce bone regeneration by osteoconduction, while these biological mediators induce regeneration by osteoinduction.¹

The need for these biological modulators resulted in the development of Platelet-Rich Plasma (PRP) by Whitmen et al., in 1997. Subsequently, a second generation platelet concentrate was developed in France by Choukroun et al., (2001) named Platelet-Rich Fibrin (PRF). Its advantages over the better known platelet-rich plasma (PRP) include ease of preparation/application, minimal expense, and lack of biochemical modification (no bovine thrombin oranticoagulant is required).^1,5

Choukroun's Platelet-Rich Fibrin (PRF) can be considered an autologous healing biomaterial, incorporating leucocytes, platelets and a wide range of key healing proteins within a dense fibrin matrix. With its strong fibrin architecture and slow release of growth factors and glycoproteins over several days, this natural bioactive membrane can enhance soft/hard tissues healing while protecting both surgical sites and grafted materials from external aggressions.⁶

However, to our knowledge there is no report in endodontic literature regarding the use of this autologous healing biomaterial along with bone grafts in periradicular surgery despite its promise. The objective of this case report was to evaluate the bone regeneration in endodontically induced periapical lesions using PRF in combination with synthetic TCP and calcium hydroyapatite bone graft material, for a period of 9 months.

CASE REPORT

A 19-year old male patient reported to the hospital with a complaint of discharge in relation to the right maxillary incisors. Further questioning revealed a history of trauma four years back. Past dental history revealed incomplete root canal treatment due to the patient's noncompliance. On intra oral examination, a sinus opening with discharge was located distal to the apical region of the lateral incisor. Thermal and electric pulp tests showed that the central and lateral incisor did not respond to vitality tests suggesting that they were nonvital. Furthermore, the occlusal radiographs showed a well defined radiolucency in relation to 11 and 12. It was decided to perform a periradicular surgery in the region based on the above findings.

The procedure was explained to the patient in his own language and informed consent was obtained. The first step of the treatment plan was to complete root canal therapy. The surgical protocol included a routine medical history followed by blood investigations. The surgical procedure included reflection of a full thickness mucoperiosteal flap by sulcular incision and two relieving vertical incisions. Debridement of the tissues at the defect site was followed by irrigation with sterile saline solution (Figure 1). Root planing was performed on the root surface under the apical portion of the root. The root apex was cold burnished.

The PRF clot was pressed between gauze squares to obtain a membrane. The membrane was cut into fragments which were then mixed with the graft material (G-Bone, G. Surgiwear Ltd., India) (Figure 2). This was carefully placed into the cavity till the entire cavity was filled (Figure 3). Wound closure was obtained with a 3-0 black silk suture. Analgesics, Antibiotics and 0.2% Chlorhexidine mouthwash was prescribed for five days post surgically. The sutures were removed after seven days. The patient was reviewed at regular intervals of one week, and one, three, six and nine months. During the review, occlusal radiographs were taken. These follow-up visits included routine intraoral examination and professional plaque control if required. The case was evaluated clinically for edema, postoperative pain, signs of infection, untoward reaction, wound dehiscence as well as radiographically.

Clincally, the case showed moderate edematous swelling 24 hours after surgery which gradually subsided by the first week. The patient did not complain of any pain nor were they any signs of infection, untoward reaction or wound dehiscence. Radiographically, there was complete bone regeneration with evidence of a trabecular pattern at the end of nine months (Figure 4).

Protocol for obtaining a PRF clot (Choukroun's Technique)

PRF preparation requires an adequate table centrifuge and collection kit including: a 24 gauge butterfly needle and 9 ml blood collection tubes. Whole blood is drawn into the tubes without anticoagulant and is immediately centrifuged at 3,000 rpm for 10 minutes. Within a few minutes, the absence of anticoagulant allows activation of the majority of platelets contained in the sample to trigger a coagulation cascade. Fibrinogen is at first concentrated in the upper part of the tube, until the effect of the circulating thrombin transforms it into a fibrin network. The result is a fibrin clot containing the platelets located in the middle of the tube, just between the red blood cell layer at the bottom and acellular plasma at the top. This clot is removed from the tube and the attached red blood cells scraped off and discarded. PRF can be obtained in the form of a membrane by squeezing out the fluids in the fibrin clot.⁵

DISCUSSION

Bone regeneration after surgical intervention takes place in a very slow manner. Therefore, various regenerative therapies are being tried out to hasten the process. Perhaps the most commonly used technique for regeneration is the use of bone replacement grafts. However, from a biological viewpoint, a blood clot is a better space filler or ECM than all bone grafting materials. A blood clot is the host's own biologic product and is essential to tissue wound healing. A blood clot is composed of insoluble fibrin and many growth factors/cytokines such as platelet-derived growth factor (PDGF), TGF-β, vascular endothelial growth factor (VEGF), endothelial growth factor, insulin-like growth factor (IGF), and basic fibroblast growth factor (FGF). During wound healing, fibrin filaments crosslinked to fibronectin provide a provisional matrix for attachment and migration of immune cells, fibroblasts, endothelial cells and tissue cells. The degraded products of fibrin, by plasmin, are chemotactic to the host's immune cells. In addition, FGF, TGF-β, VEGF, and endothelial growth factor in blood clot promote angiogenesis to enhance tissue wound healing. Bone grafts alone without a blood clot or angiogenic factors are unlikely to be capable of promoting periapical wound healing.^1,7,8

The application of local growth factors has been studied to enhance the healing and regeneration potential of endodontic surgery. PRP, growth factors including BMPs, PDGF and EMD are the most commonly used agents.⁷

In 2001, a new family of platelet concentrate, which is neither a fibrin glue nor a classical platelet concentrate, appeared in France. This new biomaterial, called platelet-rich fibrin (PRF), has been widely used to accelerate soft and hard tissue healing. It is nothing more than centrifuged blood without any addition. This clot combines many healing and immunity promoters present in the initial blood harvest. The intrinsic incorporation of cytokines within the fibrin mesh allows for their progressive release over time (7-11 days), as the network of fibrin disintegrates.^5,9,10

According to Simonpieri et al (2009), the use of this platelet and immune concentrate during bone grafting offers the following 4 advantages: First, the fibrin clot plays an important mechanical role, with the PRF membrane maintaining and protecting the grafted biomaterials and PRF fragments serving as biological connectors between bone particles. Second, the integration of this fibrin network into the regenerative site facilitates cellular migration, particularly for endothelial cells necessary for the neo-angiogenesis, vascularization and survival of the graft. Third, the platelet cytokines (PDGF, TGF- β, IGF-1) are gradually released as the fibrin matrix is resorbed, thus creating a perpetual process of healing. Lastly, the presence of leukocytes and cytokines in the fibrin network can play a significant role in the selfregulation of inflammatory and infectious phenomena within the grafted material.⁵

CONCLUSION

Although regular endodontic therapy can be predictably used to arrest mild to moderate defects, it might be inadequate for the treatment of disease characterized by large defects caused by endodontic infection. Many techniques and materials are available to promote regeneration, including bone replacement grafts, barrier membranes, and host modulating agents. Currently, regeneration attempts are widely variable in terms of their ability to predictably regenerate the lost tissue/bone in all types of defects or for all situations. Knowledge of the factors that can negatively affect regeneration outcomes and subsequent careful case selection can help to optimize successful regenerative attempts. Moreover, a critical need still exists for a therapy that can enhance the regeneration in a predictable fashion. This case report has made an attempt to evaluate the use of this new biomaterial in combination with bone grafts to predictably regenerate bone in periradicular defects.⁷