Introduction
Periodontitis is a multifactorial inflammatory progressive destructive disorder of the periodontium, associated with microbial dysbiosis, which untreated can lead to teeth loss and systemic effects [
1‐
7]. Although functional periodontal regeneration remains to be the ultimate goal for periodontal therapy, this endeavor is challenged by the biological intricacy of the periodontal support with the soft tissue components (periodontal ligament and gingiva) integrated and connected complexly into its hard tissues (alveolar bone and cementum) [
8‐
10]. In this context, a variety of techniques and materials have been suggested to achieve a complete healing/regeneration of lost periodontal support [
8,
11,
12].
Platelet-rich fibrin (PRF), the second generation of platelet concentrates, has been introduced as an autologous biological scaffold for periodontal therapy [
13‐
15]. It harbors a wide variety of biological mediators integrated in its fibrin matrix, including the platelet-derived growth factor (PDGF), the vascular endothelial growth factor (VEGF), the transforming growth factor beta (TGF-β), and the insulin-like growth factor (IGF) [
16‐
18], which are slowly released over its degradation time [
19]. Clinically, PRF matrices proved to enhance periodontal regeneration. In a systematic review investigating the adjunctive effects of platelet-rich plasma (PRP), PRF, enamel matrix derivative (EMD), and amnion membrane (AM) combined with bone grafts on the treatment of intra-osseous periodontal defects, PRF has shown to be the most effective regenerative adjunct [
20]. Additionally, PRF application in conjunction with open flap debridement (OFD) procedures yielded greater periodontal regeneration compared to OFD alone or to PRF in combination with bone grafting materials [
14,
21].
As a development of the original PRF protocol, a low-speed centrifugation concept was introduced to increase the platelets, leucocytes, and growth factors contained within the PRF matrix [
22‐
24], resulting in a superior in vitro growth factors release profile compared to earlier PRF preparation protocols [
25] and increased migration and proliferation of fibroblasts during wound healing [
26]. The present randomized controlled trial aimed to compare for the first time the clinical attachment level gain (CAL-gain; primary outcome), probing depth (PD-reduction), gingival recession depth (GRD), full-mouth bleeding (FMBS) and plaque scores (FMPS), radiographic linear defect depth (RLDD), and radiographic bone fill (secondary outcomes) of a low-speed PRF with open flap debridement (PRF + OFD) versus OFD alone for the treatment of intra-osseous periodontal defects of stage-III periodontitis patients.
Discussion
Periodontitis, a multifactorial chronic inflammatory disorder of the teeth supporting structures [
2], culminates in periodontal tissue destruction with horizontal and vertical osseous defects, commonly accompanied with deep residual pockets, which worsen the affected teeth prognosis [
35‐
37]. Mechanical removal of etiological and contributing factors [
38,
39] remains to be the primary step of any periodontal therapy. In this context, OFD remains to be one of the most documented evidence-based approaches for the surgical treatment of intra-osseous defects with remarkable clinical outcomes [
37,
40,
41]. Yet, although OFD could enhance clinical and radiographic parameters, histologically it mostly results in healing in the form of “repair,” with long junctional epithelium forming a new attachment over the affected cementum [
42]. Still, a restoration of the lost tooth supporting structures remains to be the utmost goal of periodontal therapy, with vertical intra-osseous defects showing greater potential for periodontal regeneration [
43,
44].
The aim of the current randomized controlled trial was to assess clinically and radiographically the periodontal healing/regenerative potential of a low-speed PRF delivered into intra-osseous defects through OFD, in comparison to OFD alone over a 9 months observation period. In the present trial, smokers were excluded to avoid the negative effects of smoking on periodontal healing/regeneration [
45,
46]. Apart from the heterogeneity in PRF preparation devices and protocols, it has been demonstrated that low-speed PRF of comparable quality can be reproduced successfully irrespective of the commercial centrifugation device when utilizing the same centrifugal speed and force [
47]. Thus, the present trial employed previously reported standard speed and force parameters to prepare the low-speed PRF [
48,
49]. Despite the advantages of a split-mouth design, including the control for confounders, as each patient would serve as his own control, as well as possible sample size reduction, a parallel design was chosen to eliminate any possibility for a systemic “carry-across” effect, in which local diffusion of the PRF enclosed growth/differentiation factors from intervention sites could influence the healing at the control sites [
50]. In the present study, CAL-gain was defined as the primary outcome, being the most universally accepted surrogate parameter for evaluating periodontal healing/regeneration [
12] and a direct prognostic factor related to true periodontal “hard” endpoints as tooth-survival [
51].
PRF, with its various and continuously evolving preparation protocols, has opened new perspectives to improve clinical outcomes of periodontal therapies over the last years [
14,
21]. Compared to conventional PRF, low-speed PRF is reported to demonstrate a significant higher accumulated release of VEGF, TGF-β1, and EGF [
22], with a growth/differentiation factors release profile superior to L-PRF or A-PRF [
25], favoring fibroblasts’ migration/proliferation during periodontal wound healing [
26]. A recent investigation demonstrated a significant healing/regenerative potential for the low-speed A-PRF + comparable to EMD in the treatment of intra-osseous periodontal defects 6 months postoperatively [
52]. Combining A-PRF + with an alloplastic mixture, composed of 70% hydroxyapatite and 30% β-tricalcium phosphate, for alveolar bone preservation/augmentation resulted in significantly less post-operative swelling and pain [
53]. Previous randomized controlled clinical trials comparing PRF [
54], titanium-prepared PRF [
32], PRF in combination with 1.2% atorvastatin [
55], or A-PRF [
56] applied with OFD versus OFD alone demonstrated enhanced periodontal healing with higher PD-reduction, CAL-gain, and radiographic defect fill in the platelets concentrate compared to the OFD groups. Similarly, in the current study, low-speed PRF with OFD significantly improved CAL-gain at 6 months as well as PD-reduction for up to 9 months. The stepwise linear regression analysis further demonstrated a significant correlation between CAL-gain and radiographic bone fill. Apart from the physical characteristics of the defect filling PRF hemostatic plug, the observed beneficial periodontal clinical outcomes can be explained relying on the release of the abovementioned growth, differentiation, and angiogenic factors as well as adhesion and coagulation biomolecules by the low-speed PRF, resulting in favorable cellular and biological effects, comprising the induction of a heightened migration and proliferation of gingival and periodontal fibroblasts [
26], as well as their increase in expression of collagen type 1, PDGF, and TGF-β [
25]. Finally, through its fibrin content, the low-speed PRF plug would represent an essential three-dimensional scaffold/framework for the resident periodontal cells, enhancing their local micro-environment during the biological healing/regeneration events.
Still, the results of the present randomized controlled clinical trial should be carefully interpreted in context of its limitations. First, the preparation of blood-derived biomaterials such as PRF requires collection of the patient’s own blood. Consequently, patients who were anxious of this procedure refused to participate in the present study. Second, blinding of participants could not be implemented due to the nature of procedure as the test group required blood sample collection. Third, although a 9-month follow-up period may be an acceptable period for evaluating healing and bone remodeling in periodontal defect, longer follow-up periods remain to be desirable to evaluate true periodontal endpoints (e.g., tooth survival). Yet, this was not feasible with the current study’s population from lower socio-economic background, visiting the Faculty of Dentistry, Cairo University, primarily for symptomatic treatment and considering repeated visits over a longer period a burden to their daily life. Fourth, despite the fact that in the current investigation a conventional UNC-15 periodontal probe was used for recording the periodontal findings, being a cost-effective modality of acceptable accuracy in the hands of a calibrated operator, the use of pressure sensitive periodontal probes could have additionally heightened the sensitivity and accuracy of the recorded surrogate parameters. Fifth, the current study did not record patient-related outcomes (e.g., postoperative pain, swelling, bleeding, outcomes related to the venipuncture). Finally, as in most clinical trials, the true nature of the achieved periodontal healing/regeneration could not be verified through a histological analysis for evident ethical reasons, but had to be indirectly assumed through surrogate clinical and radiographic parameters.
Within the limitation of the present randomized controlled clinical trial, it can be concluded that both OFD alone or in conjunction with low-speed PRF were able to produce significant improvement in clinical (CAL-gain and PD-reduction) and radiographic parameters (RLDD) in the treatment of periodontal defects 9 months post-surgically. The presence of low-speed PRF in the test group resulted in superior CAL-gain and PD-reduction and hence can be considered a viable cost-effective addition for improving periodontal healing/regeneration with OFD. Future research is required to explore possible advancements in blood collection tube compositions and their influence on the obtained low-speed PRF volume and quality [
32,
47]. Horizontal centrifugal procedures, which are postulated to enhance PRF inclusion and uniform distribution of platelets and leucocyte [
57,
58], should be further investigated with various centrifugal speed and force settings, with special emphasis on optimization of the regenerative and antibiotics/biological delivery potential of low-speed PRF (
30,
59). Finally, further studies with longer follow-up periods are needed to confirm the reported effects, especially in comparison to different PRF preparation schemes (e.g., L-PRF) or in combination with periodontal biomaterials (bone grafts or biological agents).
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