In a previous study involving patients at the dental clinic of the Detroit Receiving Hospital, 87% of teeth that initially had been recommended for surgery or extraction were spared either treatment through a combination of debridement and short-term usage of antimicrobial agents. The object of the present study was to determine what changes occurred to these teeth after 6.4 years in the maintenance phase of treatment. Patients were scheduled for maintenance therapy at three-month intervals over a period of 6.4 years. They were evaluated "annually" (that is, the patients were scheduled for annual visits) for surgical needs by a clinician who was not aware of the treatment received by the patients. Multivariate statistical models were used to determine which variables predicted subsequent surgical needs. The initial treatment benefits were sustained, as the majority of patients showed no increase in surgical needs after 6.4 years. When relapse occurred, those who were smoking when the study began and an increased number of sessions of debridement were predictors. Surgical needs were reduced when metronidazole was dispensed after the first and second annual examinations.