Background Guided tissue regeneration procedures provide predictable reconstruction of periodontal tissues in the treatment of furcation involvements in animals and huamns. This study was to compare long-term effectiveness of two different types of polylactic acid (PLA) membranes on periodontal regeneration in surgically created class Ⅱ furcation defects in dogs. Methods Full thickness mucoperiosteal flap was raised on the buccal aspects of the experimental teeth and class Ⅱ furcation defects having 5 mm vertical dimensions were created on mandibular premolar Ⅲ and IV on each quadrant. The exposed root sudaces were thoroughly planed and PLA membranes were placed over the experimental defects on both sites. One site received liquid polymer membrane (LPM), and resorbable periodontal mesh (RPM) membranes were applied to the other site. The animals were sacrificed at 7 months after surgery and the specimens were processed for histological evaluation. Results The average length of new attachment formed on the treated roots in both groups ranged from 3. 02mm to 4.5mm. Complete bone filling was observed at the furcation sites. No statistically significant differences were found between two membranes in any of the parameters (P＞0. 05). Conclusion This study demonstrates favorable regenerative outcomes by the use of two different types of PLA membranes that could be used as altatives for guided tissue regeneration (GTR).