Thirty-five studies were selected for the systematic review. A total of 3932 single implants were included at the beginning of studies. Thirty-one implants were removed before loading and 91 implants after loading. The overall implant loss rate was 3.1 %. Implant losses were concentrated on the period between loading and 2-year follow-up, and, after a stable period, increased after 5-year follow-up. The mean marginal bone loss at single-tooth implants was well within 0.2 mm/year, i.e., acceptable annual bone loss by the implant success criteria. However, considerable amounts of single implants suffered a marginal bone loss at implant more than 0.2 mm/year. Fistula was a frequent biological complication in the early studies. The most frequent technical problem was a screw loosening, but its frequency was reduced after the use of a gold screw and torque controller.

Within the limits of this study, the complications of single implants might be underestimated due to the lack of information about the biological and technical complications available in the relevant literature.