The aim of this investigation was to evaluate the healing following guided tissue regeneration of bone defects distal to the mandibular second molars after surgical extraction of soft tissue-impacted, mesioangularly inclined third molars. After the impacted third molars were extracted, 15 sites were treated with polyglycolic acid/polylactic acid bioresorbable membranes plus scaling and root planing (SRP) of the distal surface of the second molars (test sites); 15 sites were treated with SRP alone (control sites) according to a split-mouth design. At 12 months after surgery, the placement of barrier material was shown to have resulted in statistically significant differences in clinical attachment level and bone gain compared to control sites.