Long-Term Comprehensive Results of Four-Implant-Supported Overdentures and Fixed Complete Dentures: A Systematic Review and Meta-analysis.

This systematic review and meta-analysis evaluates medium-term clinical outcomes of four-implant-supported overdentures (IODs) and full-arch fixed restorations (IFRs) in edentulous maxillae, focusing on implant survival rate (ISR), prosthesis survival, marginal bone loss (MBL), and complications over at least five years. Analysis of 16 studies including 5,568 implants found that IFRs demonstrated higher weighted ISR (98.5%) and prosthesis survival (99.9%) compared to IODs (ISR 94.5%, prosthesis survival 85.0%). IODs showed less MBL at five years (–0.27 mm) than IFRs (–1.20 mm), though baseline differences limit direct comparison. Mechanical complications were more frequent in IODs, primarily retention loss, whereas IFRs most commonly experienced prosthesis or tooth fractures; biologic complications, mainly peri-implant mucositis, occurred more in IODs. The review highlights predictable medium-term outcomes for both modalities but notes the need for direct comparative studies, longer follow-up for IFRs, and standardized reporting to better inform clinical decision-making.