Purpose: The aim of this noninterventional, retrospective study was to benchmark the outcomes of patients with partial fixed prostheses supported by implants treated at the University of Toronto at least 10 years earlier. A study protocol for assessing outcomes on like patients developed at the University of Bern, Switzerland, was followed.
Materials and methods: All patients who had received at least one implant before 2002 were considered eligible to be included in the study (n = 298). The treatment histories were recorded from the patient chart of the participants, or from the participants' dentists by consent. Calibrated clinicians examined the study participants clinically and radiologically and recorded peri-implant mucosal status and observable technical and mechanical failures. Past adverse events were identified in the patient charts. Independent assessors measured bone levels on digitized radiographs. Statistical analysis included descriptive statistics at implants, teeth, and study participant levels, respectively.
Results: Of the 298 eligible patients, 121 attended a clinical examination (41%), while 12 declined (4%). The 121 study participants had received 321 implants between 1983 and 2001. The implants showed a success rate of 88.9% and a survival rate of 94% after an average of 17.5 years (SD 5.2, range 10 to 28 years). Approximately 5% of the surviving implants showed signs, or were associated with a prior history, of peri-implantitis. The distance from the implant shoulder to the first bone contact varied from -3 mm to 7 mm (mean = 1.52 mm [SD 1.57], median = 2.2 mm). Approximately half of the study participants had experienced at least one defect of their superstructure, representing a 52% "success rate," while the survival rate was 70%. The majority were very satisfied or satisfied with the treatment (102/121).
Conclusion: A high proportion (94%) of conventional machined Brånemark System implants placed between 1983 and 2001 remained in function after an average of 17.5 years. The original superstructures predominantly fabricated as prefabricated acrylic teeth and acrylic resin reinforced with a cast palladium-silver alloy core were still in place for 70% of the participants, and 48% of the superstructures had never undergone any form of repairs.