Implant and prosthesis failure rates with implant-supported mandibular overdentures: a systematic review

Abstract: Purpose The purpose of the present study was to assess the clinical outcomes of mandibular overdentures supported by dental implants (ISMO - implant-supported mandibular overdenture) based on a systematic review of the literature.   Materials and methods An electronic search, limited to studies published between 2018-2021, was performed in three databases, supplemented by hand searching of selected journals. Eligibility criteria included clinical human studies, either randomized or not, reporting case series of patients rehabilitated with ISMO. Interval survival rate (ISR) and cumulative survival rate (CSR) of implants and prosthesis were calculated in life-table survival analyses.   Results Sixty studies were included in the review, which reported 2261 ISMOs, supported by 4495 implants. A total of 111 implants and 191 ISMOs failed. The correlation between the survival rate of implants and the number of implants was very weak. Patients with less implants presented higher prosthesis failure rates than patients with more implants per prosthesis. There was no influence of the attachment system on the implant failure rates. The estimated CSR for the implants and the prostheses were 92.2% and 75.6%, respectively (23-year period). Replacement of attachment components was very often needed, as well as relining of the ISMO base. Complete transverse fracture of the ISMO was the most common technical complication.   Conclusion Using only one implant to support a mandibular overdenture is risky and should be avoided. In addition, metal reinforcement of the prosthesis base is recommended to minimize or prevent ISMO fractures, a common technical complication.