Nima Farshidfar, Karol Al�� Apaza Alccayhuaman, Nathan E Estrin, Paras Ahmad, Anton Sculean, Yufeng Zhang, Richard J Miron
The aim of this comprehensive review was to evaluate comparative studies on horizontal and fixed-angle centrifugation methods for preparing platelet-rich fibrin (PRF). Furthermore, additional studies utilizing horizontal PRF (H-PRF) were systematically investigated. This overview review article offers deeper insights into the advantages of H-PRF when compared to fixed-angle methods across a wide range of regenerative medical and dental applications. A comprehensive search was conducted in PubMed and Web of Science up to December 5, 2024. Grey literature was also searched via Google Scholar for additional relevant studies, and reference lists of eligible studies were screened for further potential inclusion. All in vitro, in vivo, and clinical studies that utilized horizontal or swing-out centrifugation to prepare solid or liquid PRF, along with their subfractions such as the buffy coat, platelet-poor plasma (PPP), or heated variants like albumin gel or albumin gel with liquid PRF (Alb-PRF) as interventions, were included in this study. A total of 75 studies were included. Thirteen studies directly compared horizontal centrifugation to fixed-angle centrifugation for producing PRF, while the remaining 62 studies were non-comparative and focused on expanding the uses and clinical applications of H-PRF. These studies spanned categories such as cell concentrations, fibrin matrix structure, growth factor release, antibacterial and anti-inflammatory properties, and regenerative applications in bone, periodontal, cartilage, skin, hair, regenerative endodontics, corneal defect repair, wound healing, and soft tissue regeneration. Of the studies comparing horizontal to fixed-angle centrifugation, 84.6% favored horizontal centrifugation, while 15.4% found no difference. None of the studies favored fixed-angle centrifugation. Additionally, more optimized methods for concentrating liquid-PRF (C-PRF) using horizontal centrifugation and extending the resorption properties of PRF-ranging from 2 to 3���weeks to membranes lasting 4 months through an albumin denaturation process were-further discussed. Based on these findings, it remains logical to utilize H-PRF in clinical practice owing to the greater superiority in results from the majority of studies. Nevertheless, further comparative clinical studies are needed to support these findings. While the current evidence is limited and further clinical trials are warranted, several studies have now indicated that horizontal centrifugation, compared to fixed-angle, results in higher cell concentrations, more uniform cell distribution, and increased growth factor release. These advantages suggest that the use of H-PRF may lead to enhanced clinical outcomes when the application of PRF is indicated. Since horizontal centrifugation can also lead to better cell separation, it should also be the preferred method for producing C-PRF and Alb-PRF for clinical applications.
