Marco Del Corso

Sinus Floor Augmentation With Simultaneous Implant Placement Using Choukroun's Platelet-Rich Fibrin as the Sole Grafting Material: A Radiologic and Histologic Study at 6 Months

BACKGROUND Sinus augmentation with simultaneous implant placement without bone graft material is a hotly debated technique. This technique could be improved and secured by the use of an autologous leukocyte- and platelet-rich fibrin (PRF) (Choukrouns technique) concentrate. The objectives of this study were to assess the relevance of PRF clots and membranes as the sole filling material during a lateral sinus lift with immediate implantation using radiologic and histologic analyses in a case series. METHODS Twenty-five sinus elevations with simultaneous implantation were performed on 20 patients with Choukrouns PRF as the sole filling biomaterial. For each patient, a presurgical exam and a 6-month post-surgical radiologic exam were performed with a panoramic x-ray and three-dimensional volumetric computed radiography (VCR) to evaluate the subsinus residual bone height and the final bone gain around the implants. In nine patients, 6 months after the sinus lift, bone biopsies were collected on the buccal wall of the alveolar ridge at the level of the osteotomy window, and evaluated by histomorphometry. RESULTS In this study, 41 implants from three different systems with different screw designs (Biomet 3I Nanotite, MIS Seven, Intra-Lock Ossean) were placed. All implants were inserted in residual bone height between 1.5 and 6 mm (mean +/- SD: 2.9 +/- 0.9 mm). The final bone gain was always very significant (between 7 and 13 mm [mean +/- SD: 10.1 +/- 0.9 mm]). No implant was lost. After radiologic analyses, the position of the final sinus floor was always in the continuation of the end of the implant. All biopsies showed well organized and vital bone. CONCLUSIONS From a radiologic and histologic point of view at 6 months after surgery, the use of PRF as the sole filling material during a simultaneous sinus lift and implantation stabilized a high volume of natural regenerated bone in the subsinus cavity up to the tip of the implants. Choukrouns PRF is a simple and inexpensive biomaterial, and its systematic use during a sinus lift seems a relevant option, particularly for the protection of the Schneiderian membrane.

Do the fibrin architecture and leukocyte content influence the growth factor release of platelet concentrates? An evidence-based answer comparing a pure platelet-rich plasma (P-PRP) gel and a leukocyte- and platelet-rich fibrin (L-PRF).

Platelet concentrates for surgical use are tools of regenerative medicine designed for the local release of platelet growth factors into a surgical or wounded site, in order to stimulate tissue healing or regeneration. Leukocyte content and fibrin architecture are 2 key characteristics of all platelet concentrates and allow to classify these technologies in 4 families, but very little is known about the impact of these 2 parameters on the intrinsic biology of these products. In this demonstration, we highlight some outstanding differences in the growth factor and matrix protein release between 2 families of platelet concentrate: Pure Platelet-Rich Plasma (P-PRP, here the Anituas PRGF - Preparation Rich in Growth Factors - technique) and Leukocyte- and Platelet-Rich Fibrin (L-PRF, here the Choukrouns method). These 2 families are the extreme opposites in terms of fibrin architecture and leukocyte content. The slow release of 3 key growth factors (Transforming Growth Factor β1 (TGFβ1), Platelet-Derived Growth Factor AB (PDGF-AB) and Vascular Endothelial Growth Factor (VEGF)) and matrix proteins (fibronectin, vitronectin and thrombospondin-1) from the L-PRF and P-PRP gel membranes in culture medium is described and discussed. During 7 days, the L-PRF membranes slowly release significantly larger amounts of all these molecules than the P-PRP gel membranes, and the 2 products display different release patterns. In both platelet concentrates, vitronectin is the sole molecule to be released almost completely after only 4 hours, suggesting that this molecule is not trapped in the fibrin matrix and not produced by the leukocytes. Moreover the P-PRP gel membranes completely dissolve in the culture medium after less than 5 days only, while the L-PRF membranes are still intact after 7 days. This simple demonstration shows that the polymerization and final architecture of the fibrin matrix considerably influence the strength and the growth factor trapping/release potential of the membrane. It also suggests that the leukocyte populations have a strong influence on the release of some growth factors, particularly TGFβ1. Finally, the various platelet concentrates present very different biological characteristics, and an accurate definition and characterization of the different families of product is a key issue for a better understanding and comparison of the reported clinical effects of these surgical adjuvants.

Current Knowledge and Perspectives for the Use of Platelet-Rich Plasma (PRP) and Platelet-Rich Fibrin (PRF) in Oral and Maxillofacial Surgery Part 2: Bone Graft, Implant and Reconstructive Surgery

Platelet concentrates for surgical use are innovative tools of regenerative medicine, and were widely tested in oral and maxillofacial surgery. Unfortunately, the literature on the topic is contradictory and the published data are difficult to sort and interpret. In bone graft, implant and reconstructive surgery, the literature is particularly dense about the use of the various forms of Platelet-Rich Plasma (PRP) - Pure Platelet-Rich Plasma (P-PRP) or Leukocyte- and Platelet-Rich Plasma (L-PRP) - but still limited about Platelet-Rich Fibrin (PRF) subfamilies. In this second article, we describe and discuss the current published knowledge about the use of PRP and PRF during implant placement (particularly as surface treatment for the stimulation of osseointegration), the treatment of peri-implant bone defects (after peri-implantitis, during implantation in an insufficient bone volume or during immediate post-extraction or post-avulsion implantation), the sinuslift procedures and various complex implant-supported treatments. Other potential applications of the platelet concentrates are also highlighted in maxillofacial reconstructive surgery, for the treatment of patients using bisphosphonates, anticoagulants or with post-tumoral irradiated maxilla. Finally, we particularly insist on the perspectives in this field, through the description and illustration of the use of L-PRF (Leukocyte- and Platelet-Rich Fibrin) clots and membranes during the regeneration of peri-implant bone defects, during the sinus-lift procedure and during complex implant-supported rehabilitations. The use of L-PRF allowed to define a new therapeutic concept called the Natural Bone Regeneration (NBR) for the reconstruction of the alveolar ridges at the gingival and bone levels. As it is illustrated in this article, the NBR principles allow to push away some technical limits of global implant-supported rehabilitations, particularly when combined with other powerful biotechnological tools: metronidazole solution, adequate bone substitutes and improved implant designs and surfaces (for example here AstraTech Osseospeed or Intra-Lock Ossean implants). As a general conclusion, we are currently living a transition period in the use of PRP and PRF in oral and maxillofacial surgery. PRPs failed to prove strong strategic advantages that could justify their use in daily practice, and the use of most PRP techniques will probably be limited to some very specific applications where satisfactory results have been reached. Only a few simple, inexpensive and efficient techniques such as the L-PRF will continue to develop in oral and maxillofacial surgery in the next years. This natural evolution illustrates that clinical sciences need concrete and practical solutions, and not hypothetical benefits. The history of platelet concentrates in oral and maxillofacial surgery finally demonstrates also how the techniques evolve and sometimes promote the definition of new therapeutical concepts and clinical protocols in the todays era of regenerative medicine.

Choukroun's platelet-rich fibrin (PRF) stimulates in vitro proliferation and differentiation of human oral bone mesenchymal stem cell in a dose-dependent way

BACKGROUND Choukrouns platelet-rich fibrin (PRF) is an autologous leukocyte- and platelet-rich fibrin biomaterial. The purpose of this study was to analyse the in vitro effects of PRF on human bone mesenchymal stem cells (BMSC), harvested in the oral cavity after preimplant endosteal stimulation. MATERIALS AND METHODS BMSCs from primary cultures were cultivated with or without a PRF membrane originating from the same donor as for the cells, in proliferation or osteoblastic differentiation conditions. After 7 days, the PRF membranes were removed. A series of cultures were performed using 2 PRF membranes, in order to measure the dose-dependent effect. Cell counts, cytotoxicity tests, alkaline phosphatase (ALP) activity quantification, Von Kossa staining and mineralisation nodules counts were performed at 3, 7, 14, 21 and 28 days. A last independent series was carried on up to 14 days, for a morphological scanning electron microscope (SEM) observation. RESULTS PRF generated a significant stimulation of the BMSC proliferation and differentiation throughout the experimental period. This effect was dose-dependent during the first weeks in normal conditions, and during the whole experimentation in differentiation conditions. The cultures without PRF in differentiation conditions did not rise above the degree of differentiation of the cultures in normal conditions with 1 or 2 PRF up to the 14th and 28th day, respectively. The SEM culture analysis at day 14 allowed to show the mineralisation nodules which were more numerous and more structured in the groups with PRF compared to the control groups. DISCUSSION AND CONCLUSIONS This double contradictory proliferation/differentiation result may be due to the numerous components of PRF, particularly the presence of leukocytes: any culture with PRF is in fact a coculture with leukocytes. It could be the source of differential geographic regulation processes within the culture. The combination of oral BMSC and PRF might offer many potential clinical and biotechnological applications, and deserves new studies.

Current Knowledge and Perspectives for the Use of Platelet-Rich Plasma (PRP) and Platelet-Rich Fibrin (PRF) in Oral and Maxillofacial Surgery Part 1: Periodontal and Dentoalveolar Surgery

Platelet concentrates for surgical use are innovative tools of regenerative medicine, and were widely tested in oral and maxillofacial surgery. Unfortunately, the literature on the topic is contradictory and the published data are difficult to sort and interpret. In periodontology and dentoalveolar surgery, the literature is particularly dense about the use of the various forms of Platelet-Rich Plasma (PRP) - Pure Platelet-Rich Plasma (P-PRP) or Leukocyte- and Platelet-Rich Plasma (L-PRP) - but still limited about Platelet-Rich Fibrin (PRF) subfamilies. In this first article, we describe and discuss the current published knowledge about the use of PRP and PRF during tooth avulsion or extraction, mucogingival surgery, Guided Tissue Regeneration (GTR) or bone filling of periodontal intrabony defects, and regeneration of alveolar ridges using Guided Bone Regeneration (GBR), in a comprehensive way and in order to avoid the traps of a confusing literature and to highlight the underlying universal mechanisms of these products. Finally, we particularly insist on the perspectives in this field, through the description and illustration of the systematic use of L-PRF (Leukocyte- and Platelet- Rich Fibrin) clots and membranes during tooth avulsion, cyst exeresis or the treatment of gingival recessions by root coverage. The use of L-PRF also allowed to define new therapeutic principles: NTR (Natural Tissue Regeneration) for the treatment of periodontal intrabony lesions and Natural Bone Regeneration (NBR) for the reconstruction of the alveolar ridges. In periodontology, this field of research will soon find his golden age by the development of user-friendly platelet concentrate procedures, and the definition of new efficient concepts and clinical protocols.

The relevance of Choukroun's platelet-rich fibrin and metronidazole during complex maxillary rehabilitations using bone allograft. Part I: a new grafting protocol.

Extensive bone grafting remains a delicate procedure, because of the slow and difficult integration of the grafted material into the physiological architecture. The recent use of platelet concentrates aims to improve this process of integration by accelerating bone and mucosal healing. Choukroun’s platelet-rich fibrin (PRF) is a healing biomaterial that concentrates in a single autologous fibrin membrane, most platelets, leukocytes, and cytokines from a 10 mL blood harvest, without artificial biochemical modification (no anticoagulant, no bovine thrombin). Whether used as a membrane or as fragments, PRF allows a significant postoperative protection of the surgical site and seems to accelerate the integration and remodeling of the grafted biomaterial. These properties are particularly helpful for vestibular bone grafting on the alveolar ridges. Moreover, it provides a very high quality of gingival maturation.A small quantity of a 0.5% metronidazole solution (10 mg) can also be used to provide an efficient protection of the bone graft against unavoidable anaerobic bacterial contamination. This article describes a new technique of total maxillary preimplant bone grafting using allograft, Choukroun’s PRF membranes and metronidazole. This first part focused on the preimplant reconstructive treatment using allogeneic bone granules. PRF membranes are particularly helpful to protect the surgical site and foster soft tissue healing. This fibrin biomaterial represents a new opportunity to improve both the maturation of bone grafts and the final esthetic result of the peri-implant soft tissue.

The Relevance of Choukrounʼs Platelet-Rich Fibrin and Metronidazole During Complex Maxillary Rehabilitations Using Bone Allograft. Part II: Implant Surgery, Prosthodontics, and Survival

Extensive bone grafting remains a delicate procedure, due to the slow and difficult integration of the grafted material into the physiological architecture. The recent use of platelet concentrates aims to improve this process of integration by accelerating bone and mucosal healing. Choukrouns platelet-rich fibrin (PRF) is a healing biomaterial that concentrates in a single autologous fibrin membrane, most platelets, leukocytes, and cytokines from a 10-mL blood harvest, without artificial biochemical modification (no anticoagulant, no bovine thrombin). In this second part, we describe the implant and prosthetic phases of a complex maxillary rehabilitation, after preimplant bone grafting using allograft, Choukrouns PRF membranes, and metronidazole. Twenty patients were treated using this new technique and followed up during 2.1 years (1–5 years). Finally, 184 dental implants were placed, including 54 classical screw implants (3I, Palm Beach Gardens, FL) and 130 implants with microthreaded collar (46 from AstraTech, Mölndal, Sweden; 84 from Intra-Lock, Boca Raton, FL). No implant or graft was lost in this case series, confirming the validity of this reconstructive protocol. However, the number of implants used per maxillary rehabilitation was always higher with simple screw implants than with microthreaded implants, the latter presenting a stronger initial implant stability. Finally, during complex implant rehabilitations, PRF membranes are particularly helpful for periosteum healing and maturation. The thick peri-implant gingiva is related to several healing phases on a PRF membrane layer and could explain the low marginal bone loss observed in this series. Microthreaded collar and platform-switching concept even improved this result. Multiple healing on PRF membranes seems a new opportunity to improve the final esthetic result.

Shedding light in the controversial terminology for platelet-rich products: Platelet-rich plasma (PRP), platelet-rich fibrin (PRF), platelet-leukocyte gel (PLG), preparation rich in growth factors (PRGF), classification and commercialism

A recent series of letters were published in JBMR-A about platelet concentrates for surgical use, where both terminology and content of these materials were hotly debated. The definition and classification of the platelet concentrate products are indeed very important issues, as many misunderstandings are widely spread in the large literature on this topic. These techniques were initially gathered under the name ‘‘platelet-rich plasma (PRP),’’ in reference to the generic term used in transfusion hematology, but this name is too general for the qualification of the many products developed now. In the first letter, Everts et al. insisted on the presence of leukocytes in most platelet preparations for surgical use. These authors explained a very important truth that many PRPs were in fact leukocyteand platelet-rich plasmas (LPRPs), and that the presence of leukocytes in these surgical adjuvants may be highly beneficial. They thus, introduced the term of ‘‘platelet-leukocyte–rich plasma (P-LRP).’’ Moreover, they pointed out that the two activation forms of the product (liquid platelet suspension or gelified fibrin-platelet clot) have different characteristics, and that the concentrates activated with a fibrinogen-cleaving agent (thrombin, batroxobin) should be named in fact as ‘‘platelet-leukocyte gels (PLG).’’ In this letter, these authors resumed the clarification process of the platelet concentrate definitions started in 2006. However, their proposals for terminology were not complete and have been improved and systematized in the recent publication of a wide classification system for these products. The first concern is that all PRPs do not contain leukocytes. Many PRPs obtained from cell separator units or from the Anitua’s preparation rich in growth factors (PRGF) subfamilies do not contain leukocytes and were classified as pure PRP (P-PRP). On the contrary, PRPs containing leukocytes were classified as L-PRP: this acronym seems obviously more logical and reader-friendly than P-LRP, but we agree that a consensus should be found to solve this issue once for good. The second issue is related to the gel form terminology. ‘‘Platelet gel’’ and ‘‘PLG’’ are too general terms. Indeed, products with a high-density fibrin network also exist and were classified as ‘‘platelet-rich fibrin (PRF),’’ some with leukocytes [leukocyteand platelet-rich fibrin (L-PRF)] and some without leukocytes [pure platelet-rich fibrin (P-PRF)]. All these PRFs are only available in the form of a very dense fibrin gel, while PRP gels are never so strong and dense. We thus believe that the activated form of P-PRP or L-PRP should simply be named ‘‘P-PRP gel’’ and ‘‘L-PRP gel’’ to differentiate them from the products of the PRF families. In the second letter, Anitua et al. agreed that the recent development of many different techniques with various platelet and leukocyte contents led to a confusing jungle of terms and products. This notion of ‘‘jungle of platelet concentrates’’ was already pointed out some years ago, when the main confusion between PRPs and the first PRF appeared. Anitua et al. were right in their call for the definition of a relevant terminology but their approach was unfortunately partisan. First, Anitua et al. claimed that leukocytes should be avoided in platelet concentrates for surgical use, to avoid the proinflammatory effects of the proteases and acid hydrolases contained in white blood cells, particularly when injected in tendons. However, these authors did not justify their statement with scientific evidence; to sustain their claim, Anitua et al. cited Ref. 9 describing very positive anabolic effects on tendon cells obtained with a PRP, . . . but the PRP described in this study was in fact a leukocyte-rich PRP. This question of the leukocyte content within platelet concentrates for surgical use is in fact an old debate. There is however actually no proof that the leukocytes within these surgical preparations might have undesirable side effects. On the contrary, several studies showed that L-PRPs have antimicrobial effects, but no undesirable inflammatory reactions have been observed with L-PRPs

Optical Three‐Dimensional Scanning Acquisition of the Position of Osseointegrated Implants: An in vitro Study to Determine Method Accuracy and Operational Feasibility

PURPOSE Manufacturing complex prosthetic framework on osseointegrated implants requires precision at every step of execution. The purpose of this study was to verify the possibility of applying the technology of image acquisition to determine the spatial position of osseointegrated implants. MATERIALS AND METHODS An optical three-dimensional scanning technique was employed: its measurement systematic error (bias) was calculated by comparing the results with the detection on a coordinates measuring machine. Measurements were carried out on master casts by doing an in vitro simulation of intraoral conditions. RESULT This study showed that the bias error value of the three-dimensional optical acquiring system was situated between 14 and 21 microm. CONCLUSION As far as the accuracy is concerned, it seems possible to use the three-dimensional image acquisition technology as a valid alternative to traditional impression-making procedures. However, the bias levels obtained in this in vitro study will have to be confirmed in a clinical trial.

The Use of Leukocyte- and Platelet-Rich Fibrin During Immediate Postextractive Implantation and Loading for the Esthetic Replacement of a Fractured Maxillary Central Incisor

I mplant-supported restoration of the maxillary anterior segment that is biologically, functionally, and esthetically acceptable following traumatic injuries in the maxillary anterior segment is always complex. Careful extraction of the fractured root, residual labial bone preservation, proper flap design, ideal positioning of the implant, appropriate softtissue contour, and the crown emergence are all important steps necessary to achieve a predictable, stable, functional, and esthetic success. However, healing of the tissues is always difficult to control and the development of new techniques and materials to improve these treatments is still necessary. The use of platelet concentrates is an interesting approach. Platelet concentrates for surgical use are widely used and continuously investigated in oral and maxillofacial surgery. The objective is to gather platelet growth factors and to inject them on a surgical site to stimulate the healing process. A significant percentage of the literature is focused on the platelet-rich plasma (PRP) families. PRP is a liquid platelet suspension often activated into a platelet-rich gel (like fibrin glues). Another technology called leukocyteand platelet-rich fibrin (L-PRF) allows for the preparation of strong fibrin membranes enriched with cells (activated platelets, leukocytes, circulating cells) and platelet growth factors. This autologous healing biomaterial is free of additives (no anticoagulant during blood harvest, no chemicals for activation), simple, inexpensive, and quick to prepare (15 minutes for all steps). This technique is specifically adapted to the practical needs in daily implant dentistry. Several articles have reported the use of these L-PRF membranes for the stimulation of bone and 1 Private practice, Turin, Italy. 2 Private practice, Ra’anana, Israel. 3 Clarion Research Group, Clarion, Penn. Department of Restorative Dentistry, State University of New York at Buffalo, Buffalo, NY. 4 LoB5 Unit, Research Center for Biomineralization Disorders, School of Dentistry, Chonnam National University, Gwangju, South Korea. Department of Stomatology, Oral Surgery, and Dental and MaxilloFacial Radiology, School of Dental Medicine, University of Geneva, Geneva, Switzerland. * Corresponding author, e-mail: LoB5@mac.com DOI: 10.1563/AAID-JOI-D-12-CL.3802