###### Abstract  
This overview aimed to evaluate the methods, quality, and outcomes of systematic reviews (SRs) conducted to investigate the effects of platelet-rich fibrin (PRF) in dental sockets on promoting bone regeneration and soft tissue healing and diminishing the incidence of pain, swelling, trismus, and alveolar osteitis after tooth extraction. An electronic search without date or language restriction was done in PubMed/MEDLINE, Cochrane, and Web of Science until March 2020. Eligibility criteria included SRs that assessed the effect of PRF for human alveolar socket preservation. The quality assessment of the included studies was performed using AMSTAR 2 guidelines. The protocol of this overview was recorded in PROSPERO under the number CRD42018089617. The search and selection process yielded 13 studies published between 2011 and 2018. The analysis of the studies showed inconclusive data for the effect of the PRF and the dimensional changes. There is no definitive evidence for the impact of using PRF alone on bone regeneration in post-extraction sockets. The use of PRF improves soft tissue healing and reduces pain, bleeding, and osteitis in post-extraction sockets. alveolar socket preservation; platelet-rich fibrin; PRF; growth factors; tooth extraction +
Footnote †: journal: Medical  
the horizontal width than in the vertical height. The majority of the resorption process occurs during the first six months of the post-extraction period, but it continues throughout the rest of the patient's life [3,4]. There are many different approaches for bone regeneration, such as mesenchymal stem cells, nano biomaterials, Bone Morphogenetic Proteins ( BMPs), and some bioactive molecules like melatonin and simvastatin. The role of mesenchymal stem cells [5], oral-derived stem cells [6], and dental-derived mesenchymal stem cells [7] have been reported for bone regeneration with the potential to significantly influence bone and periodontal treatment in the future. Nanostructured calcium phosphates have been extensively used in dentistry and medicine as a bone substitute. With an excellent biocompatibility and osteoconductivity, nanomaterials have been widely investigated for their application in the field of bone tissue engineering because of their dimensional similarity to human bone tissue. In addition, nanostructured biomaterials have an increased surface area and roughness, aiding in the adsorption of neighboring proteins and cells and acting as a carrier for drug delivery system [8]. Platelet-rich fibrin (PRF) is a second generation of the platelet concentrate with the presence of platelets and leukocytes in a dense fibrin matrix that does not necessitate an activator before use. It is prepared from non-anticoagulated blood undergoing single centrifugation [9,10]. As it is a reservoir of platelets, leukocytes, cytokines, and immune cells, PRF was reported to permit the slow release of cytokines (transforming growth factor, platelet-derived growth factor, vascular endothelial growth factor, and epidermal growth factor), which play a critical role in angiogenesis, tissue healing, and cicatrization [10, 11, 12, 13]. Previous systematic reviews (SRs) suggested that positive and favorable effects of PRF exist in dental sockets on promoting bone regeneration [1,2,9,14,15,16,17] and soft tissue healing [1,14,18,19], although another SR [20] showed no beneficial role in bone healing after tooth extraction. Notwithstanding previous SRs suggesting that the local application of PRF after a tooth extraction is a suitable method for reducing pain, swelling, and the incidence of alveolar osteeitis [1,14,17,18,20], the benefit of autologous platelet concentrate on decreasing pain in extraction sockets is still not measurable. In addition, PRF should be recommended for local application into the sockets for patients undertaking complicated surgical extraction [17].