POSEIDO 2013.1(1).17-27 Dohan Ehrenfest

Platelet concentrates for surgical use are autogenous regenerative preparations, produced by the centrifugation of the patient own blood sample. Most techniques are often regrouped inappropriately under the historical term of Platelet-Rich Plasma (PRP). Since 15 years, their use dramatically increased in many surgical fields, particularly in oral and maxillofacial surgery. The literature on this topic is considerable, but the published results are often contradictory. It is very difficult to sort and interpret the available data, due to a large number of preparation techniques, terminologies and forms of these materials, and the endless list of potential applications. This consensus conference of the Periodontology, Oral Surgery, Esthetic and Implant Dentistry Organization (POSEIDO) was established to support a classification system of these products, in order to improve and clarify the publications on this topic. Four main families of preparations can be defined, depending on their cell content and fibrin architecture: Pure Platelet-Rich Plasma (P-PRP), such as cell separator PRP, Vivostat PRF, PRGF-Endoret or E-PRP; Leukocyteand Platelet-Rich Plasma (L-PRP), such as Curasan, Regen, Plateltex, SmartPReP, PCCS, Magellan or GPS PRP; Pure Plaletet-Rich Fibrin (P-PRF), such as Fibrinet; and Leukocyteand Platelet-Rich Fibrin (L-PRF), such as Titanium-prepared PRF and Intra-Spin L-PRF System. P-PRP and L-PRP exist in an inactivated liquid form, and can be activated and transformed respectively into a P-PRP gel and a L-PRP gel. This terminology will serve as a basis for future works to be published in the POSEIDO journal and as a first step for further research on the topic. Keywords. Fibrin, fibrin tissue adhesive, Platelet-Rich Plasma, platelet, leukocyte. 18 Special Review: Dohan Ehrenfest DM, et al. (2013) ISSN 2307-5295, Published by the POSEIDO Organization & Foundation under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported 
(CC BY-NC-ND 3.0) License. 1. What are platelet concentrates for surgical use? Platelet concentrates for surgical use are autogenous products prepared through the centrifugation of a blood sample of the patient [1]. The concept of these technologies is to collect and gather the most active components from the blood sample platelets (rich in growth factors), fibrin and sometimes leukocytes and to prepare them in a clinically usable form. These preparations can be solutions or gels and can be injected or placed in a surgical site, on a wound or in an injured area, in order to regenerate the damaged tissues [2,3]. In most of these techniques, blood is collected with anticoagulant and then processed following a 2-step centrifugation [4]. The first step of centrifugation is used to separate the blood in 3 layers following a gradient depending on their weight: red blood cells at the bottom of the tube, acellular plasma (called platelet-poor plasma, PPP) at the top of the tube, and a whitish layer (sometimes called buffy coat, like in transfusion science) rich in platelets and cells between the 2 other layers. The red blood cells are then discarded and the second step of centrifugation is used to collect only this buffy coat and some acellular plasma. The final liquid platelet suspension is called Platelet-Rich Plasma (PRP) in transfusion medicine, and the term was used to regroup the many families of platelet concentrates for surgical use [1]. This platelet suspension can be injected in an injured site (for example in tendons or articulations in sport medicine)[5,6] or activated with bovine thrombin (or calcium chloride, or equivalent platelet activator)[7,8]. The activation of the suspension provokes the platelet growth factors release and the polymerization of fibrinogen into fibrin, to form a platelet gel similar to a fibrin glue that can be used on a surgical site or a wound [9]. This is the general description of the production of platelet concentrates, but many variations of the production exist. Particularly for the subfamily called Leukocyteand Platelet-Rich Fibrin (L-PRF), blood is taken without anticoagulant, processed with a one step centrifugation and no platelet activator is needed [10]. The philosophy of these treatments is in fact to concentrate and use the positive effects of the actors of the coagulation process. Platelets, fibrin and leukocytes act naturally in synergy in order to promote the wound healing and tissue regeneration, and the concept of platelet concentrates for surgical use is to multiply this coagulation/regeneration effect on a surgical site or wound. In the history of these techniques, researchers have focused alternately on the fibrin matrix, the platelets, the growth factors and more recently on the leukocytes and circulating stem cells [3], and the terminology of these materials has evolved following these trends [11]. 2. History of the terminology