This study is the first to investigate the effect of leucocyte platelet rich fibrin (L-PRF) combined with perforated membrane in order to treat infrabony defects and assess their combined effect in clinical attachment level gain and filling of base of the defect (BD). The main hypothesis was that if the L-PRF act as a chemoattracttant for a higher number of periosteal derived periodontal cells (PDPCs) and gingival mesenchymal stem cells (GMSCs) encouraging their passage through the membrane perforations.

A randomized (controlled) clinical trial which included forty sites with intrabony interproximal defects (2- or 3-wall) premolar/molar teeth assessed for clinical parameters. The four treatment modalities were randomly allocated by a predetermined computer generated randomization list (www.randomizer.org) into four equal groups; Group I (control group) open flap debridement (OFD): included intrabony defects treated by open flap debridement (OFD).Group II perforated membrane (PM): included intrabony defects treated by perforated membranes.Group III Leucocyte-platelet rich fibrin (L-PRF): included intrabony defects treated by leukocytes platelet rich fibrin (L-PRF). Group IV Leucocyte-platelet rich fibrin + perforated membrane (L-PRF + PM): included intrabony defects treated by Leucocyte platelet rich fibrin & perforated membranes.

Inclusion Criteria:

• Both genders aged from 18- 60 years.
• Patients free from any systemic diseases that may contra-indicate periodontal surgery (Ahmed Y. Gamal et al., 2014).
• Two- or three-wall intrabony defects in premolar/molar teeth without furcation involvement, that are measured from the alveolar crest to the defect bottom in diagnostic periapical radiographs of ≥ 3 mm (Reynolds et al., 2015).
• Probing depth ≥ 5 mm and clinical attachment loss ≥ 4 mm at the site of intrabony defects 4 week after the phase one therapy (Ahmed Y. Gamal et al., 2014).
• Free from any periapical pathosis.
• Patients willing and able to return for multiple follow up visits and perform oral hygiene instructions.
• Absence of occlusal interference, mobility and open interproximal contact.
• Good fulfillment to plaque control instructions following initial therapy.

Exclusion Criteria:

• Smokers.
• Pregnant and breast feeding females.
• Periodontal surgical treatment in the previous 12 months at the involved sites. (A. Y. Gamal et al., 2016)
• Persistence of gingival inflammation after phase I therapy.
• Vulnerable groups as handicapped, mentally disabled, prisoners and orphans.