Twenty-seven mandibular class III furcation defects were treated in 27 subjects using a regenerative therapy that included citric acid root conditioning and coronally positioned flaps secured by crown-attached sutures. In addition to this therapy, 13 of the 27 defects received freeze-dried, decalcified allogenic bone grafts. The effect of these therapies was evaluated from soft tissue probing measurements, including furcation probings to determine soft tissue closure of the defects. At 6 months postsurgery, the mean vertical probing depth reduction and the mean probing attachment level gain in the furcation area were 2.6 mm and 2.2 mm for the non-grafted defects and 1.9 mm and 1.5 mm for the grafted defects. One of the 14 non-grafted defects and 3 of 13 grafted defects were judged to show soft tissue clinical closure by a panel of 3 independent examiners. No statistically significant differences were observed between defects treated with or without bone grafts.