For patients having periodontal intrabony lesions, three treatment modalities were executed to evaluate the effect of protecting Leukocyte rich -Platelet Rich Fibrin harvests (applied in the bony defects) with resorbable collagen membranes. Clinical Outcomes recorded were the Plaque index (PI), Gingival index (GI), probing depth reduction (PD), Clinical attachment level (CAL), and radiographic defect depth changes.

For the biochemical evaluation: levels of PDGF-BB and VEGF obtained from crevicular fluid by Perio-Paper strips were assessed using ELIZA.

• Patients having 2-3 osseous bony wall infrabony periodontal lesions are enrolled in the present study. They have to be free from any systemic disease that contraindicates periodontal surgeries.
• Baseline data are obtained including the GI, PI, PD, CAL and preoperative paralleling periapical radiographs.
• Full thickness mucoperiosteal flaps are elevated and thorough debridement of the periodontal bony defect is performed.
• for OFD group; following debridement and saline irrigation, wound closure proceeds.
• for the L-PRF group; L-PRF is prepared and applied within the defect before primary closure.
• for the L-PRF + CM: similar procedure like the second group is performed but with an additional protective layer of collagen membrane on top of the defect before wound closure.
• from the second day postoperative; Periopaper strips are used to obtain a crevicular fluid sample from the sulcus
• At 6 months postoperative: the same baseline clinical measurements are obtained.

Inclusion Criteria:

• Minimum of one interproximal pocket probing depth of ≥6 mm and/or ≥5 mm CAL after 4 weeks from phase I execution
• 2 or 3 osseous wall interproximal intrabony defects that are ≥3mm in depth

Exclusion Criteria:

• Systemic diseases or conditions that contraindicate periodontal surgeries and/or affect the formed elements of the blood
• Patients who received antibiotic therapy and/or anti-inflammatory drug within the past 6 months
• Vulnerable groups
• Interdental craters and 1 wall osseous defects
• Active periapical pathosis

• The clinical data (Gingival index, Plaque index, PPD, CAL) were collected by a blinded single operator at the university outpatient clinic.
• The biochemical analysis: The biochemist received the filter papers with a label for group letter and patient number. She was didn't know which intervention was carried out for any of the samples.