A Commentary on

Leão RS, Moraes SLD, Vasconcelos BCE, Lemos CAA, Pellizzer EP.

Splinted and unsplinted overdenture attachment systems: A systematic review and meta-analysis. J Oral Rehabil 2018; 45: 647-656. doi: 10.1111/joor.12651. Epub 2018 Jun 7. Review. PubMed PMID: 29761853.

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GRADE rating

Commentary

Edentulism affects a substantial cohort of the world's population, with an estimated prevalence of 0.1% to 14.4% in younger age groups and 2.1% to 32.3% in older groups, and is significantly associated with depression and poor self-rated health.1The McGill consensus in 2002 established that mandibular two implant-retained overdentures are, not only a valid management modality but indeed a gold standard of care for edentulous patients. Nonetheless, the decision to rely on a splinted bar attachment system or an unsplinted system of ball, telescopic crown or magnetic attachments for overdenture retention remains challenging due to the range of existing variables and available options. Hence, this timely systematic review2aimed to assist the decision-making process, comparing three clinical outcomes of splinted versus unsplinted overdenture attachment systems. Implant survival rate and marginal bone loss were the primary outcomes compared, while prosthetic complications were a secondary outcome of the investigation.

The review was well performed; involving registration with PROSPERO, adherence to the PRISMA guidelines, the inclusion of three databases supplemented by hand searches, inter-examiner agreement evaluation and a clear assessment of bias using the Cochrane Risk of Bias Tool and the Newcastle-Ottawa scale. Nonetheless, the exclusion of retrospective studies and studies not published in English has limited the robustness of the review, resulting in only 380 participants in nine studies included in the review. Further complicating matters is the evident heterogeneity between the included studies, with variability in the number and type of implants, connection type, loading protocol, and follow-up periods. As a result, the authors rightly acknowledged the potential influence this evident heterogeneity and lack of standardisation had on the analyses of the meta-analysis, concluding that the findings of this review need to be interpreted with caution. Similarly, a recent Cochrane review investigating prosthodontic and patient-related outcomes of different attachment systems for maxillary and mandibular attachment systems was unable to perform any meta-analyses due to the heterogeneity of included studies. Accordingly, the Cochrane review determined that there is insufficient evidence to support improved performance and outcomes of any specific attachment system.3

The current review helps clinicians understand the limited influence splinting of overdenture attachments has on implant survival. Accordingly, as part of the decision-making process, other treatment planning considerations such as alignment and location of implants should guide the rehabilitation choice, as opposed to concerns of marginal bone loss.4 Furthermore, several other factors play a crucial role in the overall prosthetic management of edentulous patients and the intervention's long-term success. Oral hygiene,5 smoking,6 number, location and angulation of implants,7,8,9 connection type,10 existing type of bony defects11 and loading protocol12 are all potential risk factors with a more significant influence on the survival and success of implant-retained overdenture than splinting. Whilst the current review offers some insight into the limited impact of splinting on the success of treatment yet, an evidence-based, standardised guidance for prosthetic rehabilitation using overdentures remains lacking.