Effect of implant number on patient-reported outcomes in the edentulous maxilla: a systematic review and meta-analysis

Purpose This systematic review and meta-analysis evaluated changes in patient-reported outcomes following implant-supported rehabilitation of the edentulous maxilla and their association with implant number. Methods Five databases were searched through August 2026. Randomized controlled and prospective clinical studies including ≥ 10 patients and reporting patient-reported outcomes before and after treatment were eligible. Retrospective studies, studies without baseline PROM assessment, and studies involving mandibular or simultaneous maxillary and mandibular implant treatment were excluded. Risk of bias was assessed using RoB 2, ROBINS-I, or MINORS, as appropriate. Hedges’ g was analyzed using multi-level random-effects meta-analysis, with sensitivity analyses for OHIP- and VAS-based outcomes. Results Eleven studies were included. Patient-reported outcomes improved across all implant groups. Pooled effects were largest for ≥6 implants (g = 2.34; 95% CI: 1.85–2.83), followed by four implants (g = 1.13; 95% CI: 0.53–1.73); only one effect-size estimate was available for two implants. Improvement was significantly greater with ≥6 than with four implants (difference in g = 1.22; 95% CI: 0.40–2.04; p = 0.003) and remained significant when restricted to removable prostheses. Fixed and removable prostheses supported by six implants did not differ significantly. VAS-based outcomes showed a more pronounced difference than OHIP-based outcomes. Conclusions Implant-supported rehabilitation substantially improves patient-reported outcomes in the edentulous maxilla. The greatest improvements were observed with ≥6 implants, with a significant advantage over four implants, although effect magnitude varied by PROM type. Evidence for two implants remains limited.