Objectives: To evaluate the influence of implant splinting on peri-implant marginal bone level and implant failures in completely edentulous patients who have been rehabilitated with mandibular implant overdentures. Method and materials: A literature search of electronic databases (PubMed and Cochrane Central Register of Controlled Trials [CENTRAL]) was performed, with the last search conducted in July 2019. Randomized controlled trials with at least a 12-month follow-up period were selected. The review and meta-analysis were performed in accordance with PRISMA guidelines. Two comparisons were included in the meta-analysis: (1) Two-implant supported ball versus two-implant supported bar mandibular overdenture; (2): Two- versus four-implant supported bar mandibular overdenture. Results: Six randomized controlled trials fulfilled the inclusion criteria and were included in a quality assessment and meta-analysis. Pooled data revealed a nonsignificant difference in marginal bone level (I2 = 0%; P = 1; mean difference = 0.00; 95% CI −0.37 to 0.37) and implant failures (P = .24; risk ratio = 6.07; 95% CI 0.30 to 121.33) when two-implant ball overdentures were compared to two-implant bar overdentures. Similarly, there was no significant difference in marginal bone level (I2 = 59%; P = .59; mean difference = −0.16; 95% CI −0.73 to 0.41) or implant failures (I2 = 0%; P = .36; risk ratio = 2.03; 95% CI 0.45 to 9.16) when two- versus four-implant bar overdentures were compared. Conclusion: Based on the findings of the meta-analysis, there is no influence of implant splinting on peri-implant marginal bone level and implant failures for completely edentulous patients rehabilitated with mandibular implant overdentures. However, this result should be interpreted with caution due to the limited number of analyzed studies, most of them considered at unclear risk of bias. Well-designed randomized controlled trials with follow-up periods of at least 5 years are highly recommended to establish evidence with regard to the influence of implant splinting on mandibular overdentures. Keywords: dental implants, implant failure, mandibular overdenture, marginal bone loss, splinting