The persistence of intrabony defects, following non-surgical periodontal therapy, represents a risk factor for further disease progression [25]. Thus, a primary aim of individualized periodontal therapy remains to be a resolution of such defects with possible reinstitution of the lost tooth-investing and supporting structures [2, 33]. In recent years, autologous platelets concentrates were introduced as promising biological agents in the management of various periodontal defects with remarkable clinical results [34, 35], with PRF alone or in combination with bone replacement grafts reported to induce significant PPD-reduction and CAL-gain [36]. These results were primarily attributed to the PRF’s ability to enhance the periodontal wound healing events, providing three-dimensional fibrin scaffolds for cellular migration, adhesion and differentiation, through its enclosed leukocytes and platelets, in addition to its continuous delivery of a multitude of crucial growth/differentiation factors into the wound site [37–39]. Additionally, the low-speed centrifugation concept, introduced to promote a higher and more uniform distribution of platelets and leukocytes within the PRF, resulted in enhanced PRF formulations, including the liquid I-PRF. Compared to conventional PRF, I-PRF was reported to demonstrate higher concentrations of growth/differentiation factors [27] and a more sustained release of these factors over a period of ten days [5, 6]. To our knowledge the current randomized clinical trial is the first to explore the adjunctive effect of combining I-PRF with DFDBA in the surgical treatment of intrabony periodontal defects.
The amalgamation of platelets concentrates with bone grafts, in addition to enhancing the grafts’ clinical handling properties, would entrap platelets and neutrophils and release essential growth/differentiation factors in the healing periodontal site [40, 41]. Indeed, similar to earlier investigations combining PRP [42] and PRF [43] with DFDBA, or PRF with demineralized bovine bone matrix (DBBM) [44] in the management of intrabony defects, in the current study I-PRF + DFDBA as well as DFDBA alone exhibited significant CAL-gain, PPD-reduction and radiographic bone fill, with no significant differences observed between them. Similarly, the addition of a PRF membrane to bioactive glass did not enhance periodontal clinical parameters in terms of PPD-reduction and CAL-gain compared to bioactive glass alone after 9 months, although more significant bone fill was evident in the intrabony defects receiving the combined treatment after 6 and 9 months [45]. Yet, PRF used in the form of membranes with DFDBA [17] or bioactive glass [46] demonstrated significantly enhanced CAL-gain, PPD-reduction and bone fill compared with DFDBA or bioactive glass alone, allowing for the plausible assumption that, in contrast to the above-mentioned results, the growth/differentiation factors laden PRF membranes could have provide a short-term compartmentalization effect, that could augment their periodontal reparative/regenerative effects. Comparable to previous studies, demonstrating a favorable effect of PRF on soft tissue healing attributes [44, 46, 47], in the present study I-PRF + DFDBA-group exhibited an enhanced, yet non-significant, reduction in gingival recession parameters, underlying the earlier reported favorable effects of the fibrin content of I-PRF, exerting cellular adhesive and migration promoting functions, stabilizing the surgical flap, enriching the area with a multitude of essential growth/differentiation factors, thereby enhancing angiogenesis, epithelialization and soft tissue wound healing [48].
Although it was demonstrated that platelets concentrates resulting from the low-speed centrifugation concept release a higher amount of growth/differentiation over time [49], compared to A-PRF the total number of leukocytes, platelets and growth/differentiation factors could have been significantly lower in the obtained I-PRF, owing to its lesser volume [6]. This could explain the observed absence of a significant synergistic effect of I-PRF/DFDBA amalgamation on the examined periodontal parameters. A further explanation for the absence of an additional effect, similar to earlier results on the combination of EMD with DFDBA in the treatment of intrabony defects [4], could be that the biological effects of I-PRF have been masked in the amalgamate by the outstanding osteoconductive properties of the DFDBA, harboring itself an array of growth/differentiation factors in higher amounts (BMP-2, -4, and − 7, TGF-b1, VEGF, FGF-a, IGF-I) pivotal for various early and especially late stages of periodontal wound healing [50–52]. Finally, the regression model did not show associations between age, gender, number of defect walls, radiographic angle, FMPS and FMBS at baseline or follow-ups with CAL at 9 months. However, a significant direct association between RLDD at baseline and CAL was evident. Moreover, a significant inverse relationship between bone fill gain and CAL at nine months was evident, as bone gain measured radiographically is translated into a reduced attachment loss clinically.
Still, the current trial’s results should be interpreted in context of its limitations. First, the inclusion of intrabony defects with different morphologies, although randomly distributed could have affected the observed effects. A subgrouping according to the defects’ morphology, although being more informative, would have led to substantial decrease in the trial’s power. Second, the preparation of I-PRF necessitates collection of patient’s own blood. Consequently, patients who are afraid of blood sampling repelled to participate in the current trail. Third, the present study did not use the newly developed horizontal centrifugation protocol [6], which could have elevated the number of platelets and leucocytes in the I-PRF, with a more even platelets distribution. Fourth, although minimally invasive surgical techniques are currently recommended in regenerative therapeutic approaches of intrabony defects [53], these procedures were not applied in the current study due to the presence of deep intrabony defects, involving three or four sides of the root of the affected teeth, that often necessitated more extension of the flap for sufficient visibility for instrumentation and efficient debridement of the intrabony defects and the affected root surfaces [54]. Thus, instead the standard OFD was employed. Finally, as the included patients stemmed from lower socio-economical levels solely interested in a symptomatic therapy, it was not feasible to reliably include patient-reported outcomes (as self-reported pain scores) in the current investigation.
Within the limitations of current trial, it can be concluded that both treatment modalities (I-PRF + DFDBA and DFDBA alone) resulted in significant improvement in clinical and radiographic parameters 9 months post-surgically. Apart from an observed improvement in gingival recession, combining I-PRF with DFDBA did not appear to significantly augment the DFDBA’s therapeutic outcomes. Further longitudinal clinical and histological studies with larger sample sizes are needed to fully explore the regenerative potential of IPRF in combination with DFDBA and its efficacy in the treatment of intrabony periodontal defects.