In this retrospective study, the efficacy of periodontal therapy and maintenance in preventing tooth loss was evaluated. The study included 92 patients with 2310 teeth diagnosed with chronic adult periodontitis and observed over a mean period of 6.7 years, with each patient receiving surgical therapy in two or more quadrants. The group was divided into two subgroups: those who complied with the recommended maintenance schedule and those whose compliance was erratic. Individual tooth prognosis was assigned according to radiographic parameters. At the completion of active periodontal therapy, 2184 teeth were present. During the maintenance period, 44 teeth were lost due to periodontal reasons. Tooth mortality revealed a mean annual adjusted tooth loss rate of 0.07/year. Molars were the teeth most frequently lost; canines the least. The number of teeth lost in the three prognostic categories was: one (0.07%) for teeth with good prognoses, 21 (3.63%) for questionable prognoses and 22 (11.34%) for hopeless prognoses. Patients complying erratically with supportive periodontal therapy were at a 5.6 times greater risk for tooth loss following active therapy than regularly compliant patients. The results demonstrated a low tooth mortality rate in periodontal patients following active treatment combined with a strict maintenance program.