Bone and soft tissue outcomes, risk factors, and complications of implant-supported prostheses: 5-Years RCT with different abutment types and loading protocols.

BACKGROUND: Data on risk factors and complications after long-term implant treatment is limited. The aims were to evaluate the role of various fixation modes and to analyze complications and risks that affect long-term use of implant-supported partial fixed dental prostheses. MATERIALS AND METHODS: Fifty partially edentulous subjects received three Branemark TiUnite implants. Superstructures were attached directly at implant level (IL) or via abutments: machined surface (AM) and an oxidized surface (AOX, TiUnite). Implants were immediately loaded (test) or unloaded for 3 months (control). Examinations occurred over a 5-year period. RESULTS: Forty-four subjects were re-examined after 5 years. Cumulative survival rates in test and control groups were 93.9% and 97.0%, respectively. Marginal bone loss (MBL; Mean [SEM]) was significantly lower at superstructures connected to AM (1.61 [0.25] mm) than at sites with no abutment IL (2.14 [0.17] mm). Peri-implantitis occurred in 9.1% of subjects and in 4.0% of implants. Multiple linear regression indicated that increased probing pocket depth (PPD), periodontal disease experience, deteriorating health, and light smoking (</=10 cigarettes/day) predict greater MBL, whereas increased buccal soft tissue thickness and higher ISQ predict lower MBL. CONCLUSIONS: The results show that MBL was influenced by the connection type. A machined abutment, instead of connecting the superstructure directly at the implant level, was beneficial. The following factors influenced MBL: PPD, periodontal disease experience, deteriorating health, light smoking, buccal soft tissue thickness, and ISQ. The results on peri-implantitis underscore the need for long-term maintenance care. Further, the abutment material surface properties constitute additional target for strategies to minimize MBL.