Clinical Outcomes of Single Dental Implants with External Connections: Results After 2 to 13 Years

Purpose: The aim of this retrospective study was to evaluate the long-term survival rates and the frequency of complications associated with single implants and their associated restorations. Materials and Methods: A retrospective cohort study was performed in patients who received dental implants between 1997 and 2007. The cohort included patients who had a single implant restored with a cemented or screwed restoration that had been in function for more than 2 years. The cumulative implant survival rates and peri-implant conditions (marginal bone loss, pocket depth, and plaque, gingival, and bleeding indices), as well as prosthodontic maintenance requirements, were evaluated. Descriptive statistics, the chi-square test, and regression models were used. Results: Seventy-three implants were placed in 44 patients (32 women, 12 men; mean age, 48 years). All implants were available for follow-up after 2 to 13 years (mean follow-up, 60 months). The overall cumulative 5-year survival rates for implants were 95.9%, and most of the prostheses (98.6%) remained functional throughout the observation period. The overall frequency of complications was 29.6% (4.3% inflammatory, 22.5% prosthetic, 2.8% operative). The average peri-implant marginal bone loss was 1.8 mm. Peri-implant soft tissue conditions such as plaque and bleeding indices and pocket depths were also satisfactory. However, the presence of inflammation was significantly associated with pocket depth and gingival keratinized mucosa. The need to retighten loose abutment screws (21%) was the most frequent prosthodontic maintenance performed. However, all loose abutment screws occurred in prostheses retained with titanium screws, and 92.9% of the prostheses had a UCLA-type abutment. Conclusion: The implants and the associated prosthetic constructions used in this study showed excellent survival rates. However, there was a high frequency of prosthetic complications associated with titanium screws and UCLA cast abutments. Other prosthetic components may have yielded different results. Keywords: complications, dental implants, long-term survival rates, retrospective follow-up study, singletooth dental implants