Platelet Concentrates in Implantology: PRF, CGF and i-PRF — Biology, Preparation and Clinical Applications

Platelet concentrates represent an attempt to amplify the body's natural biological response to bone healing through autologous concentration of platelet growth factors. The evolution from the first generation (PRP, Platelet Rich Plasma, 1990s) to the second generation (PRF, Platelet Rich Fibrin, introduced by Choukroun in 2001) to the third generation (CGF, Concentrated Growth Factors; i-PRF, injectable PRF) reflects the progressive understanding of the relevant biological mechanisms and application challenges. Second-generation PRF overcame many of PRP's limitations — absence of exogenous anticoagulants (which in PRP interfered with natural fibrin polymerization), a three-dimensional fibrin matrix structure that facilitates surgical handling and prolonged growth factor release, and a simple preparation protocol with no chemical additives.

PRF biology centers on the fibrin matrix that forms during centrifugation of non-anticoagulated whole blood. The fibrin clot is generated by activation of the coagulation cascade inside the glass or silica-coated tube, forming a three-dimensional fibrin network that traps platelets, leukocytes, and circulating mesenchymal stem cells present in the blood. Platelets trapped in the clot progressively release their content in the days following clinical application: PDGF-AB, TGF-β1, VEGF, IGF-I, EGF — the same morphogens released by PRP but with slower, sustained release kinetics (peak release at 3-7 days from preparation, maintaining supraphysiological levels for 14-21 days according to Dohan et al., 2006). Leukocytes present in PRF — absent in leukocyte-depleted PRP — contribute pro- and anti-inflammatory cytokines that modulate the local immune response.

Centrifugation protocols decisively affect PRF composition. Choukroun's original protocol (2,700 rpm, 12 min, 11 cm radius, relative centrifugal force 400g) produces L-PRF (Leucocyte-rich PRF), characterized by a dense fibrin clot with a high concentration of leukocytes and platelets in the intermediate layer. The low-speed A-PRF protocol (Advanced PRF, Ghanaati et al., 2014) (1,300 rpm, 8 min, 200g) produces a clot with more homogeneous cell distribution and theoretically better growth factor integration. i-PRF (injectable PRF, 700 rpm, 3 min, 60g) keeps the platelet concentrate in fluid, pre-polymerization form, allowing injection or mixing with granular materials — a useful solution for hydrating Bio-Oss® before application in sinus lift or GBR. Differences between protocols in terms of clinical outcomes aren't yet sufficiently documented by good-quality RCTs.

PRF's clinical applications in implantology are numerous. In lateral sinus lift, mixing xenogenic granules with PRF (particulate bone hydrated with liquid i-PRF, then covered with a PRF membrane) has shown, in several RCTs, a 4-6 week reduction in graft maturation time compared to xenogenic material alone, with histomorphometry documenting a higher percentage of vital newly formed bone at 4 months vs. 6 months in controls (Nizam et al., Clin Oral Implants Res, 2018). In post-extraction socket preservation, filling with a PRF clot reduces crestal resorption volume compared to spontaneous healing in comparative studies, although the effect size is modest and depends on socket morphology. In peri-implant soft tissue augmentation, submucosal injection of i-PRF combined with hyaluronic acid is an emerging technique for non-surgical biotype thickening — with currently limited documentation but an interesting biological rationale.

PRF's limitations, which must be communicated to patients and considered in treatment planning, include: inter-individual variability in growth factor concentration (depending on age, drug therapy, comorbidities), lack of standardization across centrifuge systems from different brands (making comparability between studies difficult), and evidence still insufficient in quality for many clinical applications. Del Fabbro et al.'s Cochrane review (2018) on PRF in sinus lift concluded that the available evidence shows favorable trends but doesn't allow definitive recommendations for clinical practice due to insufficient methodological quality of the primary studies. PRF remains a biologically rational adjunctive tool whose clinical usefulness is still being defined, not a substitute for established surgical techniques.

CGF (Concentrated Growth Factors), developed by Rodella et al. and marketed by Medifuge (Silfradent), differs from PRF in using variable-speed centrifugation during the cycle (from 2,400 rpm to 3,000 rpm in alternating phases) which, according to its proponents, produces a fibrin matrix with superior mechanical properties and higher growth factor concentration, including coagulation factor VIII. Comparative data between CGF and L-PRF in terms of growth factor concentration and clinical outcomes are limited and of variable quality; differences documented in vitro don't uniformly translate into clinically relevant differences. The choice among available systems is currently guided mainly by the clinician's familiarity with the protocol and the availability of a dedicated centrifuge in the practice, pending adequately powered comparative trials.