Long-Term Treatment Outcomes in Edentulous Patients with Implant Overdentures: The Toronto Study

Purpose: Few long-term studies on overdentures report both implant and prosthodontic outcomes. The aim of this prospective study was to report long-term prosthodontic- and implant-related treatment outcomes of patients treated with design-specific implantsupported overdentures. Materials and Methods: Between 1982 and 1992, 45 consecutively treated patients received a total of 47 overdentures (42 mandibular and maxillary) supported by Brånemark implants. Prospective clinical and radiographic data were collected over the observation period; this study presents the most recent treatment outcomes. Results: Thirty patients (mean age 70 years) with 32 prostheses attended the final recall visit, with 67% of patients followed for 15.53 years (range 10 to 19 years). Six implants failed, and the prosthetic plan and implant cumulative survival rates were both in excess of 90%. Mean marginal bone loss around implants after the first year of loading was small (0.05 mm/year), although the individual variation was high. Linear regression analysis of bone loss indicated that gender, bicortical stabilization, bone quality, and healing time were predictors of bone loss for the first year of loading but not for the ensuing years. Prosthetic maintenance included fractured components, denture relining, and replacement of prostheses. On average, the longevity of overdenture prostheses was 12 years, and laboratory relining was necessary every 4 years. Conclusion: This study confirmed the long-term outcome success of patients treated with design-specific overdenture prostheses supported by Brånemark implants. However, prosthetic maintenance was required, a fact that should be discussed with patients prior to treatment.