O-Ring and Bar-Clip: A Comparative Analysis of Retention in Overdenture Prostheses - A Systematic Review.

Introduction: Mandibular implant-supported overdentures (IODs) show higher retention than conventional complete dentures. However, there is no consensus on the best attachment to ensure resistance to vertical displacement. The most used are o-ring and bar-clip. This systematic review answered "Which type of attachment for overdenture prosthesis provides higher retention: o-ring or bar-clip?

Methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) was followed and registered in the International Prospective Register of Systematic Reviews (PROSPERO). The search was applied to 5 databases and grey literature. The selection process occurred in two blinded steps by the reviewers following the eligibility criteria: a randomized clinical trial comparing retention between o-ring and bar-clip in IODs. The risk of bias was analyzed by RoB II.

Results: 206 articles were found, and after removing the duplicates 136 were evaluated by title and abstract of which 24 were selected for full reading, 5 met the eligibility criteria, and all had a high risk of bias. The bar-clip provided higher retention than o-ring in four studies.

Conclusions: The bar-clip system provides a higher retention rate than the o-ring. In addition, the selection of attachment systems is dependent on the patient's anatomical-functional and economic conditions.