Retrospective cohort study of rough-surface titanium implants with at least 25 years' function

Background: The longitudinal clinical outcomes over decades contribute to know potential factors leading to implant failure or complications and help in the decision of treatment alternatives. Methods: The cases of all patients who received dental implants treated with titanium plasma-sprayed surfaces and whose prostheses were set in the period 1984-1990 at seven private practices were retrospectively analyzed. The cumulative survival rate, the cumulative incidence of peri-implantitis, and the complication-free prosthesis rate were calculated with Kaplan-Meier survival curves, and the factors' influence on implant survival rate and the incidence of peri-implantitis were determined by a single factor in univariate analyses and multivariate analyses. Results: A total of 223 implants and 106 prostheses were applied to 92 patients, and approx. 62% of the implants and patients dropped out over the 25 years following their treatment. The cumulative survival rates of the implants at 10, 15, and 25 years were 97.4, 95.4, and 89.8%, respectively. A significant difference was observed in the implant position. The cumulative incidences of peri-implantitis at 10, 15, and 25 years were 15.3, 21.0, and 27.9%, respectively. Significant differences were observed in the gender, implant type, and width of keratinized mucosa around the implant. The cumulative survival rates of mechanical complication-free prostheses at 10, 15, and 25 years were 74.9, 68.8, and 56.4%, respectively. The difference in the type of prosthesis resulted in significant differences. Conclusions: The high rate of dropout during follow-up indicates the difficulty of determining long-term (> 25 years) prognoses. The gender, location, and width of keratinized mucosa affected the development of peri-implantitis, resulting in late failures. Implant-supported overdentures were frequently repaired. Tooth implant-supported prostheses are not recommended for long-term survival.