Abstract Background The existence of mesenchymal stem cells (MSCs) in Schneiderian membrane has not been determined. The aim of this study is to investigate whether there are MSCs in Schneiderian membrane. and the effect of platelet-rich fibrin (PRF) on osteogenic differentiation of these cells and on new bone formation in maxillary sinus after maxillary sinus floor elevation. Methods... https://parisnaturalfoodes.shop/product-category/honey-comb/