Purpose: To analyze the current evidence on bone loss in the posterior edentulous mandible restored with complete dentures (CDs), two-implant-supported overdentures (2-IODs), or four-implant-supported overdentures (4-IODs).
Materials and methods: A search was conducted in the Ovid MEDLINE, Embase, Web of Science, CINAHL, and Cochrane databases for clinical studies comparing bone loss in posterior edentulous mandibles restored with CDs, 2-IODs, or 4-IODs. A meta-analysis was performed using statistical software to estimate the mean differences in bone loss with 95% CI. The level of significance was set at P < .05.
Results: The search strategy identified 2,806 articles, of which 14 met the inclusion criteria. The meta-analysis included 7 two-arm studies comparing CDs vs 2-IODs or 2-IODs vs 4-IODs. No statistically significant difference was found in bone loss between 2-IODs and CDs (mean difference -0.25 [95% CI -0.85 to 0.36]; P = .43), whereas bone loss was significantly lower with 4-IODs than with 2-IODs (mean difference -0.96 [95% CI -1.86 to -0.06]; P = .04). Overall, the data were highly heterogenous (I2 > 74%).
Conclusion: 4-IODs can benefit the patient by decreasing bone loss in the posterior edentulous mandible. However, 2-IODs may not be superior to CDs in reducing bone loss in the posterior mandible. A validation of these results is needed through well-designed RCTs.