A comprehensive clinical review of platelet-rich fibrin (PRF) and its role in promoting tissue healing and regeneration: part 3

Platelet-rich fibrin (PRF) is a patient blood-derived living biomaterial with applications in a wide range of fields, including implant dentistry, periodontics, oral surgery, and regenerative endodontics. Improving one’s understanding of the clinical indications of this material will facilitate the ability to enhance the therapeutic applications of PRF in these fields, and this is the purpose of this article.

Introduction

Key treatment objectives in dental implantology, periodontology, and oral surgery are the prospect of having new therapies, biomaterials, and bioactive surgical additives available that will improve success and predictability of patient outcomes in soft and bone tissue healing and regeneration.

PRF, a patient blood-derived and autogenous living biomaterial, is increasingly being investigated and used worldwide by clinicians as an adjunctive autologous biomaterial to promote bone and soft tissue healing and regeneration. The gold standard for in vivo tissue healing and regeneration requires the mutual interaction between a scaffold (fibrin matrix), platelets, growth factors, leukocytes, and stem cells (Kawase, 2015). These key elements are all active components of PRF and, when combined and prepared properly, are involved in the key processes of tissue healing and regeneration, including cell proliferation and differentiation, extracellular matrix synthesis, chemotaxis and angiogenesis (neovascularization) (Dohan, et al., 2012; 2014). An improved understanding of the development, biological and physiological properties, and characteristics of PRF in tissue healing and regeneration over the past 2 decades has led to more successful therapeutic applications, especially in the fields of implant dentistry, periodontology, and oral surgery.

Methodology, search strategy, and inclusion criteria

An electronic MEDLINE® (PubMed®) and Google Scholar search was performed for all articles on platelet-rich fibrin (PRF) and platelet concentrates up to May 2016. The search was complemented by an additional hand search of selected journals in oral implantology, oral surgery and periodontal, as well as gray literature. The reference lists and bibliographies of all included publications were also screened for relevant studies. The search was limited to the English language. Randomized controlled trials (RCTs), controlled clinical trials (CCTs), case reports, case series, prospective, retrospective and in-vitro/in vivo studies were included in the narrative review. Animal studies were excluded from this review.

Where and how can I use PRF?

A general rule of guidance is to use PRF in surgical situations where protection and stimulation of healing and regeneration is critical and where the prognosis for tissue repair is poor or potentially compromised in the absence of a tissue regeneration scaffold and addition of growth factors.

Implant dentistry

Most of the PRF clinical research in implantology is currently focused in the fields of improving clinical outcomes with sinus floor elevations using PRF as sole grafting material, simultaneous with implant placement (Ali, et al., 2016; Simonpieri, et al., 2011) or SFE using a combination of PRF and bone allograft (FDBA) prior to implant placement (Choukroun, et al., 2006; Tatullo, et al., 2012).

Other focus areas of clinical research are use of PRF in alveolar ridge preservation (socket augmentation) (Hauser, et al., 2013), peri-implant tissue healing (Boora, et al., 2015), and improving implant stability (Öncu and Alaaddinoõglu 2015) (Table 1).

In vitro studies have shown PRF-induced gene expression of the early and late markers of osteogenesis stimulates bone and soft tissue healing (Clipet, et al., 2012). This finding suggests that PRF is indicated in numerous clinical applications, such as socket augmentation, jump gap filling during immediate extraction and implant placement, and stimulation of bone and soft tissue healing during bone augmentations or during sinus elevation.

Sinus floor elevation using PRF as sole or combination graft biomaterial

A systematic review showed that PRF used as a sole filling material in SFE with simultaneous implant placement is a simple technique with promising results (Ali, et al., 2016; Kanayama, et al., 2016). Various clinical case reports describe the lateral approach for sinus floor elevation using only PRF as the grafting material (Mazor, et al., 2009; Simonpieri, et al., 2011; Tajim, et al., 2013) (Figures 1A-1C).

The PRF membrane is recommended as an inexpensive and easily handled substitution biomaterial during sinus elevation to reduce the healing time before loading. It is a cheap and easily handled material with healing properties. Its fibrin matrix properties and ability of slowly releasing growth factors make it an ideal replacement biomaterial to replace xenogenic and expensive collagen membranes in some situations (Mazor, et al., 2009).

The review also suggests that PRF combined with a bone allograft or other bone substitutes accelerates graft maturation and decreases the healing period before implant placement. (Figures 2A-2E) The latter finding has also been confirmed by other clinical trials and case studies (Choukroun, et al., 2006; Tatullo, et al., 2012; Zhang, et al., 2012; Bölükbas, et al., 2013).

Various case studies have demonstrated that PRF membranes can be used successfully as a protective barrier to cover the sinus membrane during grafting procedures (Diss, et al., 2008; Toffler, et al., 2010; Kanayama, et al., 2014) (Figure 3). PRF membranes also represent an easy and successful method to cover sinus membrane or osteotomy window to protect the Schneiderian membrane, to facilitate wound closure, and to enhance healing (Ghetiu, et al., 2015). Cases have also been reported showing that A-PRF membrane can be used as a healing barrier when perforations or tears of the Schneiderian membrane occur (Diss, et al., 2008; Toffler, et al., 2010).

Alveolar ridge preservation (socket augmentation) for early or late implant placement

Use of PRF membranes to fill the socket after tooth extraction has shown to improve alveolar bone healing and preservation of the alveolar crest width. PRF plugs or membranes can also be used to fill extraction sockets, even when associated with compromised extraction sockets (Peck, et al., 2011), severe cystic destructions, or after cyst enucleations (Choukroun, et al., 2006; Magremanne, et al., 2009) to allow early bone and gingival regeneration required for implant placement. Clinical and histological findings suggest that filling a fresh extraction socket with PRF provides a viable therapeutic alternative for implant site preparation (Zhao, et al., 2011).

Alternatively, PRF can also be mixed with a bone substitute to fill the socket and used as a protective cover over the grafted socket (Figures 4A-4G). This is particularly important when gingival wound closure is impossible or difficult with the sutures (Del Corso, et al., 2012).

The purpose of the PRF membrane is not only to stimulate gingival healing, but also to protect the bone graft from the oral environment and to maintain it within the extraction socket, like a biological barrier. It is suggested that this technique negates the need for using more complex flaps and GBR protocols to close and augment extraction sockets.

Immediate post-extraction implant place-ment and jump-gap augmentation — peri-implant healing

PRF can be considered as a healing biomaterial with potential beneficial effect on peri-implant tissue and can be used as a therapeutic adjuvant with immediate implant placement in the clinical scenario of one-stage, single-tooth implant placement procedure in maxillary anterior region (Del Corso, et al., 2012).

With immediate implant placement, the peri-implant jump gap can be augmented with PRF clot (A-PRF or L-PRF) or solution (i-PRF) mixed with a bone substitute (Rao, et al., 2013) (Figures 5A and 5B).

In the latter case study, it is suggested that the augmented jump gap is covered with cross-linked collagen membrane, overlaid by a double layer of PRF and the flap closed by sutures. Studies have demonstrated that the use of leukocyte-platelet rich fibrin (L-PRF or A-PRF) membranes for the stimulation of bone and gingival healing around the implant is particularly significant (Öncü and Erbeyo 2015) (Figures 6A-6C). The elastic consistency of the PRF membrane allows the clinician to punch a hole in the membrane to facilitate draping the membrane over the healing abutment (Figures 7A and 7B).

Augmentation of dehiscence and fene-stration defects

Case reports indicate that PRF membrane cut in pieces or i-PRF combined with bone substitutes may offer an easy and simple method of handling and delivery of a fibrin scaffold, growth factors, and cells during the augmentation of dehiscence and fenestration defects, and at the same time reduce soft tissue and bone healing time (Simonpieri, et al., 2009; 2009; Toeroek and Dohan 2013).

PRF has also been successfully used to treat fenestration defects around implants (Vijayalakshmi 2012). PRF membrane cut in pieces (Figure 8), or platelet liquid (I-PRF) (Figure 9) can be mixed with bone graft material to cover the defect. The graft is covered with a resorbable collagen membrane to maintain form and shape and to confer graft stability and space maintenance on the bone particles. PRF membrane is then placed on top of the collagen membrane to prevent tissue dehiscence and aid in soft tissue healing.

The application of PRF to GBR procedures offers several advantages including promoting wound healing, bone growth, and maturation, graft stabilization, wound sealing, and hemostasis, and improving the handling properties of graft materials.

Treatment of peri-implant osseous defects

One clinical study showed that treatment of peri-implant defects with PRF was clinically more effective than with conventional flap surgery alone, irrespective of the type of defect (Hamzacebi, et al., 2015).

In another study, a successful treatment outcome was also reported after debridement and detoxification with a Cr,CR:YCGG later, followed by filling the defect with a synthetic hydroxyapatite embedded in native blood and covered with a PRF membrane to prevent soft tissue infiltration into the grafted area. The authors concluded that the use of PRF added to the maintenance of the graft homeostasis due to release of growth factors, thus contributing to the successful outcome of treatment (Shilbli, et al., 2013).

Augmentation of alveolar ridges (horizontal and vertical) and buccal bone defects (GBR)

Several cases have been reported of successful augmentation of alveolar ridges where there is a buccal bone defect (GBR) using PRF combined with a bone substitute (Inchingolo, et al., 2010; Krasny, et al., 2011; Kim, et al., 2013; Joseph, et al., 2014) and in cases of the severely resorbed posterior mandible.

Del Corso and Dohan (2013) suggest that three layers of L-PRF membranes used alone were adequate to use as competitive interposition barrier to protect and stimulate the bone compartment, and as healing membranes to stimulate the periosteum and gingival healing and remodeling. Periosteal incisions were done on the flaps to promote their tension-free closure.

The concept of using PRF alone as a GBR barrier still raises many questions as well as limitations and needs to be investigated with robust RCTs to determine appropriate indications and relevant combinations (Toeroek and Dohan 2013). PRF liquid (i-PRF) can be injected, or PRF membrane placed above the GBR, or GTR membrane to act as an interposition barrier to protect and stimulate the bone compartment and as a healing membrane in order to improve the soft tissue healing and remodeling, and thus avoid soft tissue dehiscence.

Guided bone regeneration

Place harvested autogenous bone adjacent to the implant or defect that requires grafting. The next layer is made up of a mixture of bone grafting material with i-PRF or PRF membrane or clot cut in small pieces.

The objective of this mixture is to help the rapid vascularization of the bone grafting material through the PRF fibrin matrix making the bridge between bone particles and allowing a quick new bone growth, while the xenograft material serves as space maintainer for the regenerative volume and supports the nucleation and accumulation of newly formed bone matrix.

The bone/PRF mixture in the augmented site is covered with a cross-linked collagen membrane to maintain the bone compartment and to prevent ingrowth of soft tissue. The collagen membrane is overlaid with a double layer of PRF membranes (Figures 10A-10C). These membranes are used as a competitive interposition barrier to protect and stimulate the bone compartment, and as healing membranes to stimulate the periosteum and gingival healing and remodeling. Periosteal releasing incisions are done on the flaps to promote their tension-free closure.

Increasing implant stability and osseo-integration

Case studies suggest that PRF application into the osteotomy site (Figures 11A-11C) increases implant stability during the early healing period, as evidenced by higher ISQ values. Simple application of this material also seems to provide faster osseointegration (Öncu and Alaaddinoõglu 2015).

Periodontal surgery

Most of the clinical research in periodontology is currently focused in the fields of improving clinical outcomes with treatment of intrabony periodontal pockets, furcation defects, gingival recession defects, and healing of connective tissue graft sites in the palate (Table 2).

Intrabony and furcation periodontal defects

The regenerative and wound healing effects have been very promising with PRF treating intrabony defects (see also Table 3).

The clinical evidence is supported by several case studies reporting on the successful application of PRF to regenerate bone and gingival tissues around teeth presenting with intrabony defects and furcation lesions.

Another study has also reported on using PRF successfully as a regenerative material in cases of aggressive periodontitis (Desarda, et al., 2013).

Surgical periodontal therapy accompanying the placement of PRF in angular defects of aggressive periodontitis patients showed decreased probing pocket depth, increased attachment level, and radiographic bone fill when baseline and 9-month follow-up data was compared. Surgical reconstructive therapy with placement of PRF in angular defects can is suggested as an effective approach to enhance periodontal regeneration.

Platelet gel acts as a stabilized blood clot and therefore is recommended as a perfect filling material for natural tissue regeneration and healing. Clinically, the general concept of “natural tissue regeneration” (NTR) and natural bone regeneration (NBR) (Del Corso, et al., 2012) requires to fill the periodontal intrabony defect with L-PRF, most times in association with a bone substitute used as a solid space maintainer, and then to cover the filled intrabony defect with L-PRF membranes, used for the protection of the grafted area and as a healing booster for the soft tissues above the defects. The objective of this cover is not only to protect the blood clot and/or the filling material, like in the GTR concept, but also to promote the induction of a strong and thick periosteum and gingiva.

The boosted periosteum functions as a true barrier between the soft tissue and bone compartments, and constitutes probably the best protection and regenerative barrier for the intrabony defects. The NTR protocol is very simple and gives excellent results in most clinical situations, with no contraindication or risk of negative effects. However, in order to get the best results, the choice and the quantity of the adequate bone substitute has yet to be determined in various clinical configurations.

Theoretically, PRF can be used as a sole grafting material or in combination with bone substitutes can be used as a filling material in intrabony defects, following GTR principles. PRF membrane is a solid material with the advantage that it is easy to handle and to position in bony defects. PRF membranes can also be used as a protection membrane after the filling of the intrabony defect (Figures 12A and 12B). In comparison to GTR membranes, PRF will undergo a quicker remodeling in situ than a resorbable collagen membrane, but will promote a strong induction on the periosteum and gingival tissue due to the slow release of growth factors and other matrix proteins (Dohan 2009; Del Corso, et al., 2009; Dohan, et al., 2009).

GTR membranes are cell-proof barriers, whereas a PRF membrane is a highly stimulating matrix, attracting cell migration and preferential differentiation allowing new blood vessel formation within the matrix, and also reinforcing the natural periosteal barrier. The hard and soft tissues migrate and interact within the PRF matrix. The PRF matrix becomes the interface between the tissues and therefore avoids the migration of the soft tissues deeper within the grafted defect or augmented site. This biological characteristic is referred to as a competitive barrier.

These bioactive interactions are very important during tissue regeneration since the periosteum covers the internal part of the gingival flap and is a key actor of bone healing and gingival maturation. While GTR membranes block the periosteum healing potential and bone/gingival interactions, PRF membranes stimulate the periosteum’s regenerative properties. However, even if PRF membranes do not block the migration of the cells, no invagination of the soft tissues within the bone area was observed when PRF membranes covered a filled intrabony defect (Simonpieri, et al., 2011).

Recession defects and guided tissue regeneration (GTR)

The clinical evidence is less promising with the treatment of recession defects (Moraschini, et al., 2015; Keceliet, et al., 2015; Rajaram, et al., 2015) (Table 2). Within the limitations of available clinical trials, the clinical evidence indicates that PRF does not improve root coverage or increases the width of keratinized mucosa in Miller’s Class I and II gingival recessions, compared to other treatment modalities.

However, cases have been reported where PRF was successfully used for treating localized (Eren and Atilla 2014; Aroca, et al., 2009; Aleksic, et al., 2010; Jankovic, et al., 2010; Jankovic, et al., 2012) and multiple (Agarwal, et al., 2013) gingival recessions. Another case study reported that the use of PRF membrane along with the VISTA technique allows clinicians to successfully treat multiple recession defects with optimal esthetic results and excellent soft tissue biotype (Gupta, et al., 2015).

Palatal bandage

PRF membranes can also be used as a palatal wound bandage or protection membranes after harvesting connective tissue grafts in the palate (Femminella, et al., 2015; Kulkarni, et al., 2014; Jain, et al., 2012).

Case studies show that PRF membrane used as a palatal bandage is an efficacious approach to protect the raw wound area of a palatal donor site and significantly accelerates palatal wound healing and reduces patient discomfort and healing time (Aravindaksha, et al., 2014; Femminella, et al., 2016).

Interdental papilla augmentation

A case study reported that PRF combined with bone graft for regeneration of interdental bone may contribute towards improved clinical success with augmentation of lost dental papilla (Arunachalam, et al., 2012). The reconstructed papilla in the new position was stable when reviewed at 3 and 6 months postoperatively.

Oral surgery

Most of the evidence-based research in the field of oral surgery is primarily focused on enhancing bone healing (Singh, et al., 2012; Gurbuzer, et al., 2010; Rao, et al., 2013) and reducing postoperative complications following third molar extractions. Research is also emerging on promoting healing of apico-marginal defects in root end surgery (Table 3). Numerous case and case series studies have been reported that support the use of PRF in various clinical applications in the field of oral surgery.

Post-extraction socket augmentation and healing

The healing and remodeling of an extraction socket is highly dependent on the initial stabilization of the blood clot and the quick gingival wound closure. This can be achieved by placing fibrin plug in the socket (with or without a bone substitute) and closing with a fibrin membrane. The use of PRF as a post extraction sockets filling biomaterial is recommended as a useful procedure in order to reduce the early adverse effects of the inflammation, such as postoperative pain (Eshghpour, et al., 2014; Uyanik, et al., 2015) and to promote the soft tissue healing and bone regeneration process (Manernzi, et al., 2015).

Clinical situations where post-extraction socket augmentation with PRF is specifically indicated are for early or delayed implant placement and immediate post-extraction implant placement (Simon, et al., 2009; Simon, et al., 2011; Triveni, et al., 2012; Rao, et al., 2013; Basarli, et al., 2015).

Reduce post-extraction complications in medically compromised cases

PRF can be used to minimize post-extraction complications such as osteitis, dry or infected sockets resulting from delayed or potentially compromised healing or bleeding situations in systemic conditions such as such as with diabetics, patients receiving oral bisphosphonate medication presenting a risk of osteonecrosis of the jaws, or patients receiving anticoagulants (Sammartino, et al., 2011).

Delayed or compromised healing of extraction sockets is mostly related to an unstable blood clot within the socket. In such case a fibrin clot is simply placed in the socket, covered with a collagen plug or membrane and sutured. Placing PRF in a socket could amplify the natural coagulation process and enhance socket healing.

Prevention of periodontal complications in third molar surgery

Complex third molar extractions frequently result in critical size bone defects and compromised healing impacting negatively on the outcome of periodontal tissues distal of the second molar. When bone defects after extraction are critical-sized (and often associated with cystic lesions), using PRF as a filling material or mixing PRF with a bone substitute in order to use a significant volume of solid biomaterial for filling is considered as reliable option.

These treatments are not, however, simple dental extractions, and are often at the border of guided bone regeneration (GBR) or bone grafting. The use of a PRF as a filling material significantly promotes soft tissue healing and also faster regeneration of bone in these sites and neighboring periodontal tissues (Ruga, et al., 2011; Yelamai and Saikrishna 2014).

Closing oroantral fistulas

Oroantral communications can complicate dental surgery, particularly during extraction of a posterior maxillary root. PRF clots can be used successfully for atraumatic or minimal intervention closure of oroantral communications, thus eliminating the need to raise mucoperiosteal buccal sliding flaps (Gülen, et al., 2015). The technique for closure of an oroantral fistula using platelet-rich fibrin is described by Argawal and co-workers (2016).

Apical/root end surgery

PRF clot (gel) serves as an ideal scaffold in root-end surgical procedures to enhance soft tissue healing and bone regeneration (Kuz’minykh 2009; Singh, et al., 2013; Shivashankar, et al., 2015; Nagaveni, et al., 2015).

Other researchers (Dhiman, et al., 2015) report that PRF may not necessarily improve the outcome of treatment.

The combination of PRF membrane as a matrix and MTA can prove to be an effective alternative for creating artificial root-end barriers and to induce faster periapical healing with large periapical lesions (Kathuria, et al., 2011). It is suggested that the combination of PRF and β-TCP for bone augmentation in treatment of periapical defects is also a more effective at increasing healing time compared to using bone substitute material alone (Jayalakshmi, et al., 2012). PRF combined with an alloplastic bone substitute has been successfully used for the management of combined endodontic-periodontal lesions (Goyal 2014).

Other oral surgical applications

The use of PRF has also been reported in other therapies including: alveolar cleft grafting (Findik and Byakul 2013).

Bisphosphonate-related oral necrosis of the jaw

Recent case reports suggested that PRF might stimulate gingival healing and act as a barrier membrane between alveolar bone and the oral cavity, therefore offering a simple, though effective treatment for the closure of bone exposure in bisphosphonate-related oral necrosis of the jaw (BRONJ) (Soydan and Uckan 2014; Kim, et al., 2014; Lundquist, et al., 2008; Nørholt and Hartley 2016).

Compromised wound healing situations (diabetics)

PRF has also been used as an adjuvant in the management of problematic chronic wounds (Lundquist, et al., 2008). The authors have shown that growth factors in PRF are protected from proteolytic degradation. This may be advantageous in the treatment of chronic wounds characterized by high proteinase activity.

Regenerative endodontic therapy

Regenerative endodontic procedures are widely being added to the current armamentarium of pulp therapy procedures (Huang, et al., 2010; Hotwani and Sharma 2014; Khetarpal, et al., 2013; Li, et al., 2013).

These biologically based procedures are designed to restore function of a damaged and non-functioning pulp by stimulation of existing dental pulp stem and progenitor cells present in the root canal under conditions that are favorable to their differentiation.

Management of open apex

Recent case reports have shown that the combined use of platelet-rich fibrin (PRF), and mineral trioxide aggregate (MTA) as root filling material is beneficial for the endodontic management of an open apex (Sundar, et al., 2015; Woo, et al., 2016). It is hypothesized that the combination of MTA and PRF may have a synergistic effect on the stimulation of odontoblastic differentiation of stem cells.

Revascularization and revitalization

Revascularization is the most studied and successful approach of regenerative endodontics (Sundar, et al., 2015). Revitalization of necrotic infected immature tooth is possible under conditions of total canal disinfection combined with the additive effect of PRF (Shivashankar, et al., 2012; Nagaveni, et al., 2015). PRF is proposed as an ideal biomaterial for pulp-dentin complex regeneration because it is a potentially valid scaffold material containing leukocyte and growth factors to facilitate tissue healing and regeneration in immature necrotic teeth in children (Woo, et al., 2016).

Repair and regenerative potential of PRF and enhanced cellular metabolism with laser bio stimulation, in combination with the sealing ability of MTA enhances the clinical success outcomes in pulpotomy and apexification procedures (Sundar, et al., 2015). Revitalization, revascularization, and regenerative pulp therapies still need to be validated with robust clinical trials.

Conclusion

PRF is increasingly being investigated and used by clinicians worldwide as an adjunctive autologous biomaterial to promote bone and soft tissue healing and regeneration. PRF technology has grabbed the attention of clinicians for several reasons: PRF is derived from the patients’ own blood, is readily available, can be produced immediately at the chairside, and is easy to prepare and is easy to use.

Furthermore, PRF technology is widely applicable in dentistry, while being financially realistic for the patient and the clinician, and with virtually no risk of a rejection reaction (foreign body response).

Clinicians are using PRF extensively and successfully in various clinical applications in dental implantology, periodontology, maxillofacial and oral surgery, and lately in regenerative endodontics to promote wound healing and tissue regeneration. The use of PRF in revitalization, revascularization, and regenerative pulp therapies are currently attracting a lot of attention, and several case studies in the field of regenerative endodontics are being reported. These applications, however, still need to be validated with robust clinical trials.

One of the clinical limitations to note is the heterogeneity in the quality of platelets and blood components due to use of different PRF preparation protocols in the various studies reviewed. Irrespective of the protocol used, all studies have all reported successful outcomes with regards to soft and bone tissue healing and regeneration. It should also be noted that at this stage in time there is not a single RCT or CCT to compare the effectiveness of A-PRF or L-PRF protocols. Furthermore, in vitro studies that claim superiority or inferiority of a specific PRF preparation have yet to be validated by independent clinical trials.

The future of PRF and its applications in clinical dentistry, especially in the field of soft tissue and bone regeneration, has enormous implications, but developing and strengthening its role in dentistry is dependent on its coherence and scientific clarity. The clinical effectiveness of different PRF preparation protocols in various clinical settings remains to be validated with a greater number of independent and robust RCTs, preferably with a split-mouth design, and larger sample sizes.

Independent, coherent, and scientific validation of PRF is needed to enhance the potential of this technology, thereby extending its therapeutic applications with improved successful and predictable outcomes for the benefit of the patient. PRF technology is in its infancy and will in future have a big impact in dentistry.