Periodontitis is characterized by a chronic, multifactorial inflammatory process driven by dysbiotic plaque biofilms. It is recognized as the most common chronic inflammatory non-communicable disease in humans. The advanced and severe forms of periodontitis have an estimated prevalence of 7.4%, while milder forms can affect up to 50% of the population.

If left untreated, periodontitis can lead to tooth loss. However, it is largely preventable and treatable with mechanical non-surgical periodontal therapy. To improve periodontal healing and thus clinical attachment gain after non-surgical therapy, adjunctive bioactive formulations such as enamel matrix derivatives, sodium hypochlorite, locally delivered antimicrobials, or hyaluronic acid have recently been proposed. However, these agents are non-autologous formulations and expensive.

Platelet-rich fibrin (PRF) acts as a scaffold that inhibits the early migration of epithelial cells into the periodontal tissues. Its regenerative properties are primarily due to its ability to promote angiogenesis. This ability is attributed to the 3D fibrin matrix, which can simultaneously transport several cytokines and growth factors. These include vascular endothelial growth factor (VEGF), insulin growth factor (IGF), transforming growth factor β1 (TGF-β1) and platelet-derived growth factor (PDGF). PRF further shows antibacterial properties and accelerates soft tissue healing. So far PRF is not routinely used in periodontal non-surgical therapy.

The aim of this 6-month, split-mouth randomized clinical trial including 20 patients is to test whether PRF can improve the results after non-surgical therapy.

The primary objective of this study is to determine whether scaling and root planing (SRP) combined with the application of a platelet-rich fibrin (PRF) membrane can improve clinical outcomes. Specific outcomes to be measured include reduction in probing pocket depth (PPD), gain in clinical attachment level (CAL), improvement in plaque index, gingival index, and minimization of gingival recession (GR) compared to SRP therapy alone after 3 and 6 months. Further patients reported pain outcomes as well as bacterial profiles and inflammatory markers will be checked.

Patients presenting with periodontitis stage II-IV will be included having at least 20 teeth.

The study includes multiple timepoints: a screening visit, a visit for full-mouth non-surgical treatment with and without PRF in a split-mouth design, a 7-day follow-up visit, a 3-month follow-up visit, and a final assessment 6 months after the non-surgical therapy.

Inclusion Criteria:

• Men and women aged ≥ 18 years
• Periodontitis stage II-IV, grade A/B/C, generalized
• Presence of at least 20 teeth (excluding wisdom teeth)
• Absence of removable dentures
• Patients willing to provide written informed consent and to complete the 6- month study follow-up

Exclusion Criteria:

• Patients already participating in other clinical trials
• Periodontal treatment in the previous 12 months
• Antibiotic treatment 3 months prior to study entry
• Antibiotic prophylaxis required for dental treatment
• Current use of any medication that may affect the clinical features of periodontitis
• Pregnant/lactating
• Any condition that prevents venipuncture
• Not willing to venous puncture
• Current cancer treatment
• History of radiation in the head-neck area

Opaque sealed envelopes will held the randomisation key of which side has to be treated with PRF. After completion of the non-surgical mechanical debridement in the whole dentition, the sealed envelope will be opened. PRF will be obtained from the elbow vene and after centrifugation the PRF will be applied in the pockets ≥ 5 mm. On the control side an empty cannula will be held.