4 subjects with bilateral through-and-through mandibular furcation lesions were assessed for the healing response in terms of attachment gain following surgical debridement, root planing, citric acid demineralisation and topical application of autologous fibronectin. The results were compared with sham-operated and saline-treated contra-lateral sites. There was no significant difference in the attachment gain at sites treated with autologous fibronectin and citric acid compared with sites treated with citric acid alone.