Long-Term Retrospective Observational Cohort Study on the Survival Rate of Stepped-Screw Titanium Implants Followed up to 20 Years

Purpose: The aim of this long-term retrospective study was twofold: (1) to evaluate the survival and success rates of stepped-screw titanium implants with an airborne particle-abraded and acid-etched surface, and (2) to assess the influence of hypothetical predictors of implant failure on the survival rate. Materials and Methods: From 75 possible candidates, 67 patients contributing 346 Frialit-2 implants (DPS Frialit-2 implant system, Friadent) placed between 1997 and 2005 were retrospectively evaluated. The inclusion criteria consisted of implants placed in either native or augmented bone, rehabilitated with an implantsupported prosthesis, and radiographically documented at the time of prosthetic loading (T0). At the followup recall performed between January and October 2018 (T1), clinical and radiologic examinations were conducted to evaluate the survival and success rates. The influences of specific variables on the survival rate were subsequently investigated, including gender and smoking habits, location and size of the implants, and bone augmentation procedures. Cox regression and shared frailty models were used, with the patient representing the statistical unit. Results: A survival rate of 91.62% over a median observation time of 189 months with a range of 11 to 20 years was observed. A total of 14 out of 29 implants failed before delivery of the provisional prosthesis. Overall, the median marginal bone loss was 1.25 mm, with an annual increase of 0.12 mm. Different from the other variables, the results of the multivariate model indicated that smoking was strongly correlated with implant failure (P = .002). Conclusion: Considering the limitations of this study, stepped-screw titanium implants with an airborne particle-abraded and acid-etched surface provided a good survival rate. Smoking might be considered a relevant risk factor for implant failure. Keywords: dental implants, implant-supported prosthesis, retrospective study, rough surface, survival rate