Do Clinical Outcomes Differ Between Single- vs Two Implant- Supported Mandibular Overdentures? A Meta-analysis of Randomized Controlled Trials.

PURPOSE: To examine whether mandibular overdentures supported by a single implant vs two implants have similar clinical outcomes, especially pertaining to implant survival, marginal bone loss (MBL), and prosthetic complications.

MATERIALS AND

METHODS

A systematic review and meta-analysis of randomized controlled trials (RCTs) was conducted. Scientific databases (PubMed, Embase, Scopus, Web of Science, and Cochrane Library) were searched from inception until October 2024. These databases were searched for RCTs comparing single- implant- and two- implant-supported mandibular overdentures that reported implant failures, MBL, and prosthetic complications.

RESULTS

Eleven RCTs were included. The meta-analysis showed reduced implant failure rates with single implants at 1 year (OR: 0.33; 95% CI: 0.10, 1.15; I2 = 0%) and 5 years (OR: 0.11; 95% CI: 0.01, 2.16), but the results were not statistically significant. However, pooled subgroup analyses of studies with a follow-up period of 2 to 3 years indicated a significantly reduced implant failure rate with a single implant compared to two implants (OR: 0.12; 95% CI: 0.03, 0.54; I2 = 0%). No significant differences between the implant failure rates were observed between the two groups based on implant loading protocols. Meta-analysis also showed that there were no significant differences in the risk of MBL between single- and two-implant groups (MD: -0.15; 95% CI: -0.31, 0.01; I2 = 43%). The pooled analysis also showed that the risk of overdenture fracture, relining, and metal housing reattachment did not differ significantly between single- and two-implant groups.

CONCLUSIONS

Evidence from a limited number of RCTs, mainly with small sample sizes, indicates that single- implant-supported mandibular overdentures may have a tendency to cause implant failures at a lower rate than two- implant-supported mandibular overdentures. The risk of MBL and prosthetic complications may not differ between the treatment modalities.