A retrospective study on clinical and radiological outcomes of oral implants in patients followed up for a minimum of 20 years
BACKGROUND: Very long-term follow-up of oral implants is seldom reported in the literature. PURPOSE: To assess oral implant failure rates and marginal bone loss (MBL) of patients followed up for a minimum of 20 years. MATERIALS AND METHODS: Implants placed in patients followed up for 20+ years were included. Descriptive statistics, survival analyses, generalized estimating equations were performed. Three-hundred implants were randomly selected for MBL. RESULTS: 1,045 implants (227 patients) were included. Implant location, irradiation, and bruxism affected the implant survival rate. Thirty-five percent of the failures occurred within the first year after implantation, and another 26.8% in the second/third year. There was a cumulative survival rate of 87.8% after 36 years of follow-up. In the last radiological follow up, 35 implants (11.7%) had bone gain, and 35 implants (11.7%) presented at least 3 mm of MBL. Twenty-six out of 86 failed implants with available radiograms presented severe MBL in the last radiological register before implant failure. CONCLUSIONS: Most of the implant failures occurred at the first few years after implantation, regardless of a very long follow up. MBL can be insignificant in long-term observations, but it may, nevertheless, be the cause of secondary failure of oral implants in some cases.