This was a split-mouth randomized controlled trial. Patients were recruited among the ones seeking for periodontal treatment at the Post-graduate Clinic of Periodontics using the following inclusion criteria: (1) diagnosis of chronic periodontitis15; (2) presence of at least one pair of interproximal infrabony defects (2-3 walls) adjacent to vital anterior or premolar teeth; (3) absence of 2 and 3 mobility degrees16; (4) probing pocket depth (PPD)≥ 5mm; (5) full-mouth plaque score ≤ 20%17; and (6) keratinized tissue width of at least 2mm. The exclusion criteria were: (1) presence of any systemic disease that could interfere with periodontal treatment; (2) infrabony defects with trans-surgical depth ≤4mm; (3) antibiotic treatment administered during the last 6 months.