One of the main benefits of PRF is the fibrin network that promote not only blood clot formation but also tissue repair mechanisms [27]. Compared to PRP, the kinetics of growth factor release appear to be slower, thus affecting regeneration over a longer period of time [28]. More and more studies are drawing attention to the beneficial effect of leukocytes on healing as well as tissue regeneration, and not least the importance of the quality of the fibrin network. The leukocytes it contains have both anti-infective and immunoregulatory functions [29–32], but also produce significant amounts of VEGF [33]. These factors, in addition to platelet-derived angiogenesis-stimulating factors, may have a positive impact on proper blood supply of the healing wound. White blood cells are involved in the early stimulation of osteo-progenitor cells and promote the differentiation of monocytes into macrophages [16, 33–36].
Many controlled randomized clinical trials investigated the use of PRF for the repair/regeneration of periodontal intrabony defects [37–41]. All studies demonstrated that the additional application of PRF increased PD reductions and CAL gains compared to open flap debridement alone. In a recent publication the supplementation of PRF with EMD did not result in a difference between the study and control (EMD only) groups [42]. The efficacy of PRF and EMD in the treatment of intrabony defects was compared in a clinical and a cone beam computed tomography study. Based on the obtained results, both materials were effective in the treatment of intrabony defects, however EMD was significantly superior in terms of percentage defect resolution [43]. Although these clinical trials have all shown that the use of PRF results in statistically significant CAL gains and PD reduction, it is important to emphasize that histological examination would be necessary to confirm whether the obtained results correspond to a periodontal regeneration or a periodontal repair.
It has been demonstrated that the biological benefits of PRF act locally by rapidly stimulating a large number of cell types by influencing their recruitment, proliferation and/or differentiation [15]. Based on the available literature, it seems that PRF favours the regeneration of soft tissues rather than hard tissues [44]. In the treatment of intrabony defects where space maintenance is not an issue, blood clot formation alone could be enough [45], the additional use of PRF acts primarily as a scaffold, inserted into the periodontal pocket may promote tissue regeneration [17]. More research is needed to determine which factors in the PRF clots (cells/leukocytes, growth factors, or fibrin matrix) are most required to accelerate the regeneration of periodontal tissues.
Data from in vitro studies indicates that EMD may also influence periodontal wound healing by an indirect stimulatory effect on the release of growth factors during periodontal wound healing and by inhibiting or at least retarding epithelial down-growth [46].
The modification of the preparation protocol by reducing the applied centrifugation force (RCF), resulted in an improved preparation protocol for advanced PRF (A-PRF) using 208 g RCF. Compared to PRF the A-PRF clot showed a more porous structure with a larger interfibrous space, where cells (particularly platelets) were observed in even distributions throughout the entire clot, furthermore histological analysis of A-PRF has showed a significantly higher number of neutrophile granulocytes [44].
Described by Fujioka-Kobayashi et al., it has been found that the total growth factor release could be enhanced by reducing both centrifugation speed and time. A-PRF + showed similar porosity to A-PRF, furthermore over the entire clot the cellular distribution pattern it has showed evenly dispersed platelets. These observations emphasize the improved regenerative capacity of advanced PRF matrices [20].
The results of the present study obtained after six months post-surgically clearly indicate the significant improvement of the following parameters: PD, CAL, BS in both groups. No adverse reactions have been observed throughout the first six months, which clearly indicates that the use of autologus test material has been well tolerated.
As a result of surgery and cessation of inflammation, the rate of gingival recession became significantly higher in both groups compared to the baseline. Upon intergroup comparison the GR increase was found to be non-significantly different. The cause of gingival recession observed after periodontal surgery does not necessarily depend on the methods. However, the gingival biotype can significantly affect the extent of the recession. At the same time, a significant improvement in clinical probing pocket depth resulted in a significant enhancement of the clinical attachment level. In addition to the significant improvement of bone sounding values, radiographs taken with the “long-cone” technique also suggest the presence of bone filling. (Fig. 1.,2.)
There was no significant difference between the test and control groups in the first 6 months after surgery and the results obtained with both materials were similar. The amount of gingival recession seems to be lower in the control group. Thus, it appears that the clinical benefit of both treatments is not only treats intrabony defects, but also improves PD values by facilitating plaque control and maintenance. However, when interpreting these findings, we must keep in mind that currently no other data evaluating the treatment of intrabony defects with A-PRF+ / EMD is available. Therefore, direct comparisons with other studies are not possible at this point in time.
On the other hand, it also needs to be considered that the lack of a difference between the two groups can additionally be related to the rather limited number of treated defects (e.g. 15 defects in each group) and therefore, the study may not have the statistical power to rule out the possibility of a difference between the two groups. For superiority trials in the treatment of periodontal intrabony defects, a sample size of approximately 30 persons per group has been estimated to be required [47].
Finally, the present study using a new generation of PRF seems to open new horizons in the investigation of the effects of platelet-concentrates on periodontal healing. However, other randomized, clinical trials with a bigger population and with histological evaluation of periodontal regeneration will be necessary to confirm the results of this study.