In this study, 24 furcation defects in 12 patients were treated by either (1) a polylactide resorbable membrane (Guidor) plus a polyglactin mesh (Vicryl) and demineralized freeze-dried bone allograft (DFDBA), or (2) a polylactide resorbable membrane and DFDBA. All defects were reentered after 9 months. Class III furcations closed 66% of the time when treated by the first method, while the closure rate was only 33% when treated by the second method (no polyglactin mesh). Defects with a vertical opening of < or = 4 mm closed 74% of the time, while those with vertical openings > 4 mm closed only 11% of the time.