Effects of Different Centrifuged Platelet Concentrates on Bone Remodelling Around Dental Implants

Platelet concentrates obtained from blood have been used as regenerative biomaterials in periodontal surgery. Along with the migration and proliferation of osteogenic cells, platelets accelerate bone regeneration by increasing the formation of blood vessels and inducing inflammatory reactions. Experimental studies revealed that growth factors released from platelets enhance osteoblastic differentiation on the implant surface, and enlarge the contact surface of the bone and implant. Platelet-rich fibrin (PRF), a platelet concentrate, was introduced by Choukroun in 2001, and it contains a significant amount of cytokines. Advanced-platelet rich fibrin (A-PRF), discovered in 2014, is a PRF derivative with a denser leukocyte concentration and a softer consistency. Concentrated growth factor (CGF), another platelet derivative, differs from A-PRF since it contains many concentrated growth factors trapped in a more rigid fibrin structure. It was reported that both A-PRF and CGF, obtained with variable centrifuge speeds, accelerated the proliferation and differentiation of bone cells. Stimulated osteoblasts and osteocytes initiate the remodelling process by producing macrophage colony-stimulating factor and receptor activator of nuclear factor-kappa B ligand (RANKL).Previous studies reported that TNF-α initiated bone resorption independently of RANKL.Osteoprotegerin (OPG) is a soluble cytokine receptor of the TNF family and is produced by osteoblasts, fibroblasts, and a number of host cells. OPG binds to RANKL and prevents the RANKL-RANK interaction Therefore, it inhibits osteoclastic activity. The RANKL/OPG ratio is used as an indicator for estimating bone remodelling, osteoclastic activity, or osteogenesis. The interactions among cytokines, growth factors, chemokines, and chemical mediators during blood clot formation result in a complex signalling process. High concentrations of cytokines and growth factors in the wound promote the migration of macrophages, neutrophils,