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

Purpose This systematic review aims to integrate the medium-term outcomes of four-implant supported overdentures (IODs) and full arch fixed restorations (IFRs) in the maxilla. Materials and Methods The search was performed in PubMed, Embase, and Cochrane databases, complemented by manual search. The inclusion criteria were at least 10 maxillary edentulous patients restored by IOD or IFR and at least five years of follow up. RoB 2, and NOS tools were used to assess risk of bias. Implant survival rate (ISR) was calculated as primary outcome. Protheses survival rate, marginal bone loss (MBL), and complications were the secondary outcomes. Results Sixteen studies with a total of 5568 implants met the criteria (nine on IODs, seven on IFRs). The weighted ISR of IODs was 94.5% (95% CI [92.1%, 96.9%], I2:84.22%), and subgroup analysis was performed on attachment system and study type. The weighted ISR of IFRs was 98.5% (95%CI [97.4%, 99.5%], I2:77.88%). For prostheses survival, the rate of 85.0% in IODs was lower than that of 99.9% in IFRs. MBL in the fifth year was -0.27±1.31 mm in IODs and -1.20±0.76 mm in IFRs. Retention loss (0.34 per patient) and dislodgement/fracture of the acrylic teeth (0.09 per patient) were the most common complications in IODs and IFRs, respectively. Conclusions Despite the variance of baseline, IFRs had a relatively higher implant and protheses survival rate than IODs, whereas IODs had less MBL at the fifth year and higher incidence rate of complications. Both fourimplant- supported maxillary overdentures and full arch fixed restorations have predictable medium-term clinical results.