Implant-supported single-tooth restorations:: a 5-year prospective study

Background: Comparatively few studies are available reporting at least 5 years of follow-up data of implant-supported single-tooth replacements. Objective: To evaluate prospectively the 5-year outcome of implant-supported single-tooth prosthetic restorations. Material and Methods: Forty subjects (mean age 41 years), 23 males and 17 females, who required single-tooth prosthetic replacement for a missing tooth were recruited. A total of 45 self-tapping implants (Astra Tech((R)) ST-implants) - 40 in the maxilla and five in the mandible - were installed in a two-stage procedure. Abutment connection was performed 3-6 months after implant installation. Clinical and radiographic examinations were performed at the completion of the prosthetic treatment and once a year during a 5-year follow-up period. The analysis of peri-implant bone level alteration was performed on subject and implant levels and by the use of analysis of variance and binary logistic regression. Results: Three patients were lost during the 5 years of follow-up. One implant was lost after 2.5 years in function and another four implants could not be accounted for at the 5-year follow-up examination. The overall failure rate at 5 years was 2.6% (subject level) and 2.3% (implant level). The mean loss of marginal bone at the implants during the first year in function was 0.06 mm (SD 0.67) on the subject level and 0.02 mm (0.65) on the implant level. During the subsequent 4 years the annual change in peri-implant bone level amounted to -0.02 mm (0.22) on both subject and implant levels. Thus, the mean total bone level change over the 5-year interval was -0.14 mm (1.04) on subject level and -0.11 mm (1.00) on the implant level of analysis (p > 0.05). The frequency of implants with a 5-year bone loss of >= 1 mm was 13%. Approximately 50% of the implants demonstrated no bone loss. Conclusion: The present clinical trial on single-tooth replacements with the Astra Tech(R) implant system demonstrated that the bone loss during the first year of function as well as annually thereafter was small.