An in vitro comparative study to evaluate the retention of different attachment systems used in implant-retained overdentures

Aim: The aim of this in vitro study was to compare the change in the retentive force and removal torque of three attachment systems during simulation of insertion-removal cycles. Methodology: Edentulous mandibular models were made with heat-cured polymethyl methacrylate resin. Two implant replicas (CMI), of 3.75 mm diameter and 10 mm length, were placed in the intraforaminal region. Acrylic resin mandibular overdentures were fabricated and provision was made to receive three different overdenture attachment systems, prefabricated ball/o-ring attachment (Lifecare Biosystems, Thane, India), Hader bar and clip attachment (Sterngold, Attleboro, MA), and Locator ® implant overdenture attachment stud type (Zest Anchors LLC, USA). Using a universal testing machine, each of the models were subjected to 100 pulls each to dislodge the overdenture from the acrylic model, and the force values as indicated on the digital indicator were tabulated both before and after thermocycling (AT). Statistical Analysis Used: Statistical analysis comprised Kolmogorov-Smirnov test, Friedman test, and Wilcoxon signed ranks test. Results: The statistical model revealed a significantly different behavior of the attachment systems both before and AT. The ball/o-ring and bar attachments developed higher retentive force as compared to the locator attachment. The bar and clip attachment exhibited the highest peak as well as the highest mean retention force at the end of the study. The Locator ® attachment showed a decrease in retentive potential after an early peak. Conclusions and Clinical Implications: The ball/o-ring and bar and clip attachments exhibit higher retentive capacities than the Locator ® attachment over time.