This study investigates the effect of titanium-prepared platelet-rich fibrin (T-PRF) treatment on the angiogenic biomarkers in gingival crevicular fluid (GCF) in infrabony defects of patients with chronic periodontitis. In each patient, the infrabony defect of one side of arch was designated as control group (allograft), while the infrabony defect on the contralateral side of same arch was designated as test group (allograft+T-PRF).