The 2002 McGill Consensus statement indicated that a mandibular denture retained by two dental implants should be the standard of care for patients with edentulous mandibles. However, it has been estimated that implant support dentures are up to 2.4 more costly than conventional dentures. Single implant dentures were first described in 1991 and a number of studies have been conducted.
The aim of this review was to assess the survival and complication rates of single implant retained overdentures for the rehabilitation of the edentulous mandible.
Searches were conducted in the PubMed, ScienceDirect, Cochrane, Embase, LILACS, IndeMED,Opengray and NIH clinical trials databases. Prospective studies of single implant retained overdentures published in English between 1990 and 2018 were included. Two reviewers independently selected studies with data being extracted by one reviewer and verified by a second. Risk of bias was assessed using the Risk of Bias In Non-randomized Studies of Interventions (ROBINS-I) tool and the Cochrane domains based tool for randomised controlled trials (RCTs). Studies with a follow-up period of 1 year and above were included for meta-analysis. A Poisson regression model was applied to estimate the survival rates of the implant and prosthesis employed.
- 17 prospective studies (9 RCTs) were included
- Follow-up time ranged from 1- 60 months.
- Two RCTs and 6 non-randomised studies were considered to be at low risk of bias and none at high risk of bias.
- Length of implants used ranged from 7 -15mm and diameter from 3.75 – 8mm.
- 11 studies contributed to meta-analyses
- 5-year survival rate = 91.93% (95%CI; 82.80 -100%)
- 10-year survival rate = 83.95% (95%CI; 58.59 – 100%)
- Overall failure rate per 100 implant years = 6.03 (95%CI; 4.91-7.16)
|5-year survival rate (95%CI)||10-year survival rate (95%CI)|
|Immediate loading||96.67% (77.42 -100%)||83.85% (58.96 -100%)|
|Early loading||84.98% (60.96 -100%)||69.96% (21.92 -100%)|
|Delayed loading||95.43% (87.47 -100%)||91.64% (76.81 -100%)|
- The greatest number of fractures were associated with ball abutments with an event rate of 10.8 (95%CI; 10.5-11.09) per 100 prosthesis years.
- Locator abutments showed a greater number of maintenance events with an event rate of 16.84(95% CI:16.01-17.66) per 100 prosthesis years.
The authors concluded:-
Single implant-retained overdenture treatment is a cost-effective, minimally invasive and simple treatment that can be used to restore function and aesthetics to edentulous patients, with relatively high implant and prosthesis success rates and minimal complications.
A good range of databases were searched for this review but limiting the inclusion criteria to English language only many have excluded some relevant studies Only 9 of the included studies were randomised controlled trials and only 3 of the studies had a follow up period of longer than 2 years. Consequently, this is likely to be too short a time period for implant failures. We have previously looked at one of the included RCTs (Dental Elf – 4th Feb 2015) highlighting a potential issue with attrition bias in that trial and this may be a concern in other studies. The meta-analyses included both RCTs and prospective studies and of the studies contributing to the meta-analyses only 3 reported implant failures. The paper report implant survival per 100 implant years which as the authors’ note, assumes a constant rate over time which may not properly represent the clinical situation. With implants demonstrating good ten and even 20 years survival rates in other situations more high quality RCTs with longer follow up periods are needed to properly assess this treatment approach.
Padmanabhan H, Kumar SM, Kumar VA. Single Implant Retained Overdenture Treatment Protocol: A Systematic Review and Meta-Analysis. J Prosthodont. 2019Dec 18. doi: 10.1111/jopr.13133. [Epub ahead of print] PubMed PMID: 31849146.
Dental Elf -4th Feb 2015