## 3 Results
[PERSON]'s breakthrough was classified as the second generation of platelet concentrates, called L-PRF (Platelet-Rich Fibrin) concentrates, which he produced and presented in 2001 [12, 13]. Unlike previous concepts, the protocol for obtaining PRF does not require any additives; only the patient's blood, a glass tube and a centrifuge are needed to obtain a clot, and the process is physiological, using the autogenous thrombin present in the collected blood [14]. The original procedure used 10 mL plastic tubes with a glass cover on the inside, and the collected blood was centrifuged for 10 min at 3000 RPM. When the blood contacts the inside surface of the glass tube, the clotting cascade is activated; fibrinogen accumulated during the centrifugation process in the upper part of the tube, as a result of the action of thrombin, is transformed into a fibrin clot occupying the central part of the tube, inside which platelets, white blood cells and growth factors are trapped; the upper layer is platelet-poor plasma and the lower layer is red blood cells [5]. PRFM, T-PRF, liquid i-PRF, Vivostat PRF and A-PRF, A-PRF+, CGF are among the second generation formulations and are described below:  
* PRFM (Platelet-Rich Fibrin Matrix), is a method of producing platelet-rich fibrin without the use of additional bovine thrombin. In the first stage (low speed centrifugation),red blood cells are separated from platelets and plasma proteins in a 9 mL tube containing sodium citrate. In the second centrifugation, fibrinogen is converted to cross-linked fibrin containing platelets in the presence of CaCl2 [15]. * T-PRF (Titanium-prepared Platelet-Rich Fibrin): the patient's blood is collected into 10 mL titanium tubes and centrifuged without anticoagulants at 3500 RPM for 15 min [16]. * i-PRF (injectable Platelet-Rich Fibrin): from 10 mL of a patient's blood drawn into a plastic tube, centrifugation at 700 RPM for 3 min produces a liquid form of fibrin without the use of anticoagulants [17]. * A Vivostat PRF-120 mL of whole blood is collected and processed in the Vivostat Processor Unit using the \"platelet\" program. After 26 min. of centrifugation, 6 mL of preparation is obtained (without the use of thrombin) [18]. * L-PRF (Leukocyte and Platelet-Rich Fibrin) was invented by [PERSON] in 2001, and the clot was obtained by centrifuging the blood at 3000 RPM in 10 mL plastic tubes for 10 min [13]. * A-PRF (Advanced Platelet-Rich Fibrin), A-PRF+ (Advanced Platelet-Rich Fibrin +) and CGF (concentrated growth factors) will be described below. In 2014, [PERSON] and [PERSON] et al. [19] presented a modification of the original system for producing platelet-rich fibrin, called the new A-PRF (advanced platelet-rich fibrin) procedure. Blood was collected from patients and immediately centrifuged in sterile 10 mL vacuum glass tubes for 14 min at 1500 RPM. When the centrifugation speed was reduced while the process was prolonged, the researchers discovered an increase in the presence of neutrophils captured between fibrin fibers. Products of neutrophil degranulation influence the conversion and differentiation of monocytes into macrophages. In turn, growth factors secreted from macrophage granules can influence bone and soft tissue regeneration. In collaboration with [PERSON], [PERSON] et al. [20] proposed a variation of the aforementioned procedure in 2017, naming the produced product A-PRF+. Patient blood was collected into a 10 mL glass vacuum tube and centrifuged at 1300 RPM for 8 min to obtain A-PRF+. In vitro, the researchers found that the A-PRF and A-PRF+ regimens released more growth factors (e.g., PDGF-Platelet-derived growth factor, TGF-1-Transforming growth factor beta 1, EGF-Epidermal growth factor, IGF-1-Insulin-like growth factor 1) from fibrin than the original L-PRF regimen. Furthermore, A-PRF+, a platelet rich fibrin, released more growth factors than A-PRF fibrin. In 2006, another researcher, [PERSON], named his unique method of generating fibrin clots by centrifugation with varying centrifugation settings \"CGF\".