Efficacy of injectable platelet-rich fibrin in the erosive oral lichen planus: a split-mouth, randomized, controlled clinical trial

Abstract Objective Our study compared the effects of injectable platelet-rich fibrin (i-PRF) with those of corticosteroids in the treatment of erosive oral lichen planus (EOLP). Methodology This split-mouth study included 24 individuals diagnosed histopathologically with bilateral EOLP. One bilateral lesion was injected with i-PRF, whereas the other was injected with methylprednisolone acetate in four sessions at 15-day intervals. Visual analog scale (VAS) for pain and satisfaction, oral health impact profile scale-14, and the lesion size were used. Results The intragroup comparisons showed a significant decrease in VAS-pain and lesion size in both the i-PRF group (from 81.88±17.74 to 13.33±18.34, and from 4.79±0.41 to 1.88±1.08, respectively) and the corticosteroid group (from 80.21±17.35 to 23.33±26.81, and from 4.71±0.46 to 2.21±1.35, respectively) in the 6th month compared to baseline (p<0.001). Moreover, VAS-satisfaction increased significantly in both the i-PRF group (from 26.67±17.8 to 85.63±16.24) and the corticosteroid group (from 28.33±17.05 to 74.38±24.11) in the 6th month compared to baseline (p<0.001). However, no significant difference in any value occurred in the intergroup comparisons. Conclusion In patients with EOLP, both methods decreased pain and lesion size similarly, and both increased satisfaction. Therefore, the use of i-PRF may be considered an option in cases refractory to topical corticosteroid therapy. Biochemical and histopathological studies are required to reveal the mechanism of i-PRF action in EOLP treatment.


Introduction
Oral lichen planus (OLP) is a chronic inflammatory immune mediated disease of unknown cause, in which T lymphocytes attack multi-layer flat epithelial cells. 1,2 Most infiltrating lymphocytes seen in OLP are CD8+, so the condition probably results from a cytotoxic autoimmune response. 3 Furthermore, CD4+ T lymphocytes increase the cytotoxicity of CD8+ lymphocytes by infiltrating OLP lesions. The buccal mucosa, tongue and gingiva are the most frequently affected regions in the oral cavity, and the lesions can occur symmetrically, bilaterally, or unilaterally. Reticular and papular OLP lesions are often asymptomatic; however, atrophic and erosive oral lichen planus (EOLP) forms can negatively affect patients' quality of life, causing sensitivity, burning symptoms, and discomfort. 4 The treatment for OLP lesions include different pharmacological agents, such as corticosteroids, immunosuppressives, retinoids and metronidazole. 5 Corticosteroid treatment, in particular, can lead to several side effects, such as pain, bleeding, ulceration, secondary infections, perilesional linear atrophy, hypopigmentation, allergic reactions, calcification and granuloma. 4,5 Consequently, medical treatment may include different alternative therapies, such as biostimulation with diode laser, photodynamic therapy based on methylene blue, psoralen and ultraviolet A therapy (a form of photochemotherapy treatment), ozone therapy and herbal remedies with antiinflammatory properties (e.g., aloe vera, lycopene). 1 Platelet-rich fibrin (PRF) is a three-dimensional fibrin network that accelerates wound healing, immunity and neovascularization. It contains host immune defense cells (leukocytes) and promotes three important stages of wound healing: angiogenesis, immune response and epithelial proliferation. 6 In one study comparing PRF and connective tissue graft to treat gingival recession, the levels of gingival crevicular fluid proinflammatory markers (interleukin (IL)-1β and matrix metalloproteinase-8) were significantly lower in the PRF group. 7 Similar to conventional PRF, injectable PRF (i-PRF) increases the number of leukocytes and stimulates growth factor release. 8 In another study, direct injection of the lesion with growth factor-rich plasma, which is a first generation blood product and contains anticoagulants, decreased pain and improved quality of life in patients with OLP. 9 The i-PRF is an autogenous product that acts as a growth factor release system involving transforming growth factor-β (TGF-β), platelet-derived growth factor (PDGF), and vascular endothelial growth factor (VEGF). 10 Figure 1 shows the study flow chart.

Patient selection
To ensure 80% power (1 -β) with a 95% confidence interval (α=0.05), and an effect size of 1.01, and considering the lesion size scores at the 2 nd month (according to Thongprasom), the study size was estimated as 17 patients per group. 16  and who were refractory to topical corticosteroid therapy. The punch biopsy method was used for histopathological evaluation, and no volunteers had received lichen planus treatment in the previous 3 months. The baseline and 2 nd month follow-up data for 13 patients were included in our previous pilot study. 19 The exclusion criteria were: age younger than 18 years, pregnancy or breastfeeding, systemic disease (e.g., diabetes, Cushing's syndrome), coagulation disorders, smoking, infectious disease (e.g., hepatitis), use of anticoagulant drugs, psychiatric problems, dysplasia upon histopathology 16 and OLP manifestations in other mucous membranes simultaneously.
Preparation of i-PRF Venous blood was collected from each patient using a 20-mL syringe and placed in two plastic i-PRF tubes (10 mL each, without anticoagulant). The tubes were centrifuged with Intra-spin system, Intra-Lock centrifuge (Process for PRF, Boca-Raton, FL, EUA) at 700 rpm for 3 min (47 g force) to obtain i-PRF. The i-PRF was then drawn into dental injectors with 27 gauge needle tips in preparation for injection.  Thongprasom, et al. 24 (2003).

Application protocol
Specifically, a score between 0 and 5 points was assigned (score 0: no lesion, score 1: only white stria, score 2: < 1 cm 2 white line with erythematous area, score 3: > 1 cm 2 white line with erythematous area, score 4: < 1 cm 2 white line with erosive area, score 5: > 1 cm 2 white line with erosive area). The evaluation was performed just before the first injection, and at the 1 st , 2 nd , and 6 th month control sessions.

Discussion
In our study, VAS-pain levels after the last injection in the i-PRF group were lower, and VASsatisfaction levels were higher. However, the i-PRF and corticosteroid groups showed no difference regarding VAS-pain, VAS-satisfaction, or lesion size. In contrast,    In our study, the positive effects of i-PRF on VAS-pain and VAS-satisfaction levels and on lesion sizes may be due to all these features.
We decided not to perform biopsy after the treatments, since a mechanical trauma can trigger new erosive lesions in lichen planus. 3 This decision, however, impeeded the performance of histopathological evaluations. Therefore, we investigated the treatment results subjectively using the VAS and objectively using Thongprasom scoring. One limitation of our study is the fact that the systemic absorption of the corticosteroid on the contralateral lesion area has unknown side effects. However, our study used a splitmouth design, found in the literature, 30