Single vs 2 Implants on Peri-implant Marginal Bone Level and Implant Failures in Mandibular Implant Overdentures: A Systematic Review With Meta-analysis

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As a consensus, the 2-implant supported overdentures (ODs) are considered as the first choice of treatment for the edentulous mandible. In the same context, there is increased evidence supporting the use of single-implant OD. The aim of any design is to preserve the remaining structures and allow the longevity of the treatment.


To evaluate the impact of single implant vs 2 implants on the peri-implant marginal bone loss (MBL) and number of implant failures in mandibular implant overdentures.


A literature search of electronic databases (PubMed and Cochrane) was performed up to March 2016 and complemented by hand search. Randomized clinical trials (RCTs) that evaluated MBL and number of implant failures relative to single-implant mandibular overdenture (MOD) were selected. The review and meta-analysis were performed using meta-analytic statistical package and in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.


Five RCTs met the inclusion criteria for systematic review and qualitative synthesis. The observation period ranged from 12 months to 5 years in the selected RCTs. The comparison included in the meta-analysis is single- vs 2-implant MODs. Pooled data revealed that single-implant MODs significantly decreased the MBL (mean difference: 0.27, 95% confidence interval: 0.20–0.34, P < .0001, I2 = 0%) and number of implant failures (risk ratio: 3.26, 95% confidence interval: 1.18–8.97), P = .02; I2 = 0%).


Single-implant MOD was found to be better than 2-implant MOD in terms of MBL and number of implant failures. However, this result should be interpreted with caution due to limited number of analyzed studies with different loading protocols and short follow-up period.

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