The principle of guided tissue regeneration using barrier membranes has become an accepted method for the treatment of teeth with severe osseous defects and furcation involvement. A technique was developed using an expanded polytetrafluoroethylene soft-tissue patch, 1 mm thick (W.L. Core and Assoc., Flagstaff, AZ), in conjunction with an alloplast hydroxyapatite bone substitute (HA-500, 40-60 mesh) (Orthomatrix, Minneapolis, MN), for space maintenance in severe osseous defects. A case report is presented which demonstrates the successful use of this method, and includes a fourth-year re-entry procedure that illustrates the complete bone fill and obturation of a severe vertical defect and Class II furcation of a mandibular first molar.