Objective: To evaluate clinically the long-term results following treatment of deep intrabony defects with either platelet-rich fibrin gel (PRF) or an enamel matrix derivative (EMD).

Methods: Twenty six patients diagnosed with advanced chronic periodontitis, and each of whom displaying one deep intrabony defect were randomly treated with open flap debridement and with either PRF (test) or EMD (Emdogain, Straumann, Basel, Switzerland) (control). The clinical outcomes were evaluated at baseline, at six months and three years after treatment. The primary outcome variable was the clinical attachment level (CAL).

Inclusion Criteria:

1. No systemic conditions affecting treatment outcomes
2. Good oral hygiene [plaque index (PI) <1; Löe 1967]
3. Compliance with the maintenance program
4. Presence of at least one intra-bony defect with a probing depth (PD) of ≥6 mm and an intra-bony component of ≥3 mm confirmed by radiographs.

Exclusion Criteria:

• significant medical conditions: irradiation in the maxillofacial area, uncontrolled diabetes or hypertension, systemic steroid or bisphosphonate treatment, pregnancy, or lactation, infectious diseases,
• age <18 years, (3) smokers (>5 cigarettes/day),
• high residual inflammation (FMBS >25%),
• poor oral hygiene (FMPS >25%), and
• defect-related factors: furcation involvement, endo-perio defects, horizontal defects, or multi-tooth defects .