Effectiveness of mandibular overdentures supported by 1 or 2 implants: An umbrella systematic review

The authors conducted an umbrella systematic review to evaluate the methodological quality of existing reviews and compare the clinical and patient-centered effectiveness of single implant-retained mandibular overdentures (1i-MOs) with 2 implant-retained mandibular overdentures (2i-MOs).

Systematic reviews with and without meta-analyses on 1i-MO and 2i-MO were included on the basis of a comprehensive literature search performed in June 2024 across MEDLINE via PubMed, Scopus, Embase, Web of Science, Cochrane Library, and System for Information on Grey Literature in Europe via OpenGrey databases. Independent reviewers performed study selection, data extraction, and analysis. Primary outcomes were implant loss and prosthesis failure. Secondary outcomes included marginal bone loss, general complications and maintenance needs, quality of life, patient satisfaction, masticatory function, and cost-effectiveness. The Risk of Bias in Systematic Reviews tool was used to assess the risk of bias in the studies.

Of the 2,289 initial records, 8 systematic reviews (5 with meta-analyses and 3 without) met the inclusion criteria (κ = 0.90). Some meta-analyses provided strong short-term evidence favoring 1i-MO for implant loss, prosthesis failure, and marginal bone loss. However, long-term effectiveness remains uncertain due to nonsignificant results and wide 95% CIs. Patient-centered outcomes (satisfaction, quality of life, general complications and maintenance needs) were inconclusive, suggesting the need for further research. Risk of bias was low in 62.5% and high in 37.5% of the included reviews.

Although some evidence suggests 1i-MO may reduce implant loss, prosthesis failure, and marginal bone loss in the short term, results of most comparisons showed no clinically meaningful differences or were inconclusive due to nonsignificant results and wide 95% CIs. Given the considerable risk of bias in some studies, further well-designed research is needed to confirm these potential benefits.