| Objective:We are aimed to get better understanding on biological characteristics of PRF through ultrastructure observing of PRP and PRF,clinical use of PRF in dental implant and to explore the possible bone regeneration mechanisms initiated by PRF.Methods:In this report, there are two parts. The first part is a randomized observing experiment. In the experimental group,6 healthy donors (3 male,3 female) were divided into 3 groups. Whole blood was collected from them to prepare PRF, and then PRF samples were observed by optical microscope,SEM and TEM. Two donors' whole blood in control group was collected to prepare PRP, and then the samples were observed by SEM.Then compare and analysis the two's ultrastructures.In the second part,20 patients (12male,8 female, average ages 44.8) participated in the study. All the patients underwent bone defects.14 defects were filled with Bio-Oss or Bio-Oss mixed with autogenous particulate bone with artificial membrane covered in control group. PRF was covered on the transplanted bone in another 9 defects in PRF group. A total of 25 implants were inserted in all cases in the same term. Patients were recalled in 1 weeks,2 weeks,1 month,4 months,6 months. and X-ray examinations were taken prior to and after operation,in 1 months,6 months.Results:In the first part, we found that, in platelet-rich fibrin (PRF), fibrins get together for a loose solid net structure, it contains lots of platelets and leucocytes. In PRF, every platelet relates with several fibrins, it seems some fibrin straight into the platelets, this part of membrane structures of platelets that get close together with the fibrins are disappeared, some fibrin move highly responsive platelet shape and there is higher density layer of material between the membrane of platelet. In addition,in PRF platelets are not fully activated,and they are rich in a-granules.In PRP,platelets spread lots of pseudo pods and accumulate in a big cluster, a little leucocytes scatter.In the second part, we found that no infection was observed in each case. One month after the grafting procedure, soft tissue dehiscence occurred in 1 cases in control group. One month after the grafting procedures, the X-ray films in each group clearly displayed the presence of the graft particles. It appeared of inhomogeneous density with very dense areas comparable to the surrounding bone. Six months after the grafting procedures, the aspect of graft particles in PRF group appeared homogeneous with the surrounding environment, and the transverse part of the implants shows no bone resorption. In control group,We see the similar performences of bone healing. All completed restorations of implants work well.Conclusions:In the first part, the result of this study implied that PRF is a loose three-dimensional networt structure accumulated by fibrin and it contains a large number of unfully activated platelets with a-granules.Fibrin netlike structure of platelet-rich fibrin (PRF) and the physiological binding with platelets are the main differences between PRP and PRF, and are the main structural foundations for prolonging the effect of cytokines. PRF also contains lots of leucocytes which may have plenty of immunological values, and that may help reduce postoperative pain and edema.In the second part, the clinical finding suggests platelet-rich fibrin (PRF)could be used safely. The bone graft particles seemed to be active and replaced by the surrounding bone in the PRF group, it also seems that gingival soft tissue flap get mature more quickly in this group. PRF membrane can play the role of collagen membrane in some cases.During implant surgery, PRF should be used as a membrane to foster healing of wound edges and to provide a high-quality gingival maturation.
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