The Long-Term Outcomes of Maxillary Implant-Supported Overdentures: a Retrospective Study

Objectives: The objective of this study was to assess the survival rate of implants and maxillary implant-supported overdentures (MISODs), along with investigating maintenance needs, technical and biologic complications, and potential risk indicators for these complications.
Methods: This retrospective cohort study included 77 patients who received 94 MISODs supported by 416 implants between 1983 and March 2022 in a university setting. Data analyses were carried out to determine frequency of maintenance events and complications (technical and biologic. Regression analyses were performed for each type of complication and complications overall to identify potential risk factors. Cox regression analyses were used to evaluate time to event for maintenance, complications, and transition of prostheses.
Results: In this study, MISODs had a follow-up of 5.3±7.9 years (range: 1 to 34.5 years). 44% had non-splinted attachments, 55% had splinted. 9% of prostheses were supported by 2-3 implants, 60% by 4, and 31% by more than 4. The most commonly performed maintenance procedures included adjustments the intaglio surface of the prosthesis , changes of nylon inserts, and clip re-activation. Technical complications occurred in 36% of cases, including compromised function due to suboptimal retention (36%), acrylic tooth fracture (23%), and denture base fracture (14%). Biologic complications included peri-implant mucositis (55%) and peri-implantitis (44%) with differences obaserved between different attachment mechanisms. Implant failure occurred in 6% of cases before loading the prostheses, and 8% after. 36% of prostheses required transitioning to a new one after an average follow-up of 6.6 ± 7.5 years due to supporting implant failure, suboptimal retention, denture base fracture, and occlusal wear.
Conclusions: This study found no differences in technical and biologic complications between splinted and non-splinted attachment mechanisms for MISODs. However, a notable percentage of prostheses required modification or replacement due to technical complications, patient preference, and implant failure. Careful patient selection and long-term monitoring are important to minimize complications and improve treatment outcomes