Evolution of in vivo assessed retention forces in one-piece mini dental implant-retained mandibular overdentures: 5-Year follow-up of a prospective clinical trial.

Background: The evolution of retention forces in one-piece mini dental implants (MDIs) retaining implant overdentures (IODs) is of major importance, as the male parts cannot be exchanged, due to the implant design.
Purpose: To report the evolution of retention forces of one-piece MDIs, retaining mandibular IODs with ball/ O-ring attachments during 5 years assessed in vivo.
Materials and Methods: Four MDIs were installed in the interforaminal region and immediately loaded using the existing mandibular complete denture. Directly post-op, at the 1-year and the 5-year follow-up, the retention forces were assessed with a validated strain gauge at each implant site separately.
Results: At the male part, changes could only be observed at implant site 34: During the first year, there was a statistically significant increase, whereas the retention forces were decreased at the 5-year follow-up. At the female part, retention forces decreased significantly over time. Baseline values could be reestablished by exchanging the O-rings. The changes of the retention forces were more obvious in the posterior, compared to the anterior implants.
Conclusions: Retention forces at the female part decrease significantly over time, when retaining mandibular IODs by MDIs with ball/ O-ring attachments. Baseline values can be reestablished by exchanging the O-rings. At the male part, changes of retention forces depend on the implant location.
(© 2019 Wiley Periodicals, Inc.)