Dislodgement force analysis of an overdenture attachment system.

STATEMENT OF PROBLEM: The performance of a recently introduced overdenture attachment system after cyclic dislodgement is not known. PURPOSE: The purpose of this in vitro study was to compare a conventional attachment system and a recently introduced attachment system for their dislodgement forces before and after cyclic dislodgement. MATERIAL AND METHODS: Three acrylic resin models were fabricated with 2 implant analogs (4.1 mm; Zimmer Dental) in different angulations; parallel in the first, divergent by 30 degrees in the second, and divergent by 60 degrees in the third model. Six acrylic resin blocks containing 2 metal housings of 2 different LOCATOR attachments (LOCATOR Legacy [LL], R-Tx, n=3; Zest Dental Solutions) were also fabricated. LOCATOR abutment pairs (LL and R-Tx) were placed onto the analogs. Seven specimens for LL and R-Tx with pink attachments were tested for dislodgement forces, and the values were recorded before and after 1440 times (simulated 1-year use) of cyclic dislodgement using an occlusal loading simulator machine. A 3-way ANOVA was used for dislodgement force comparison before and after cyclic dislodgement for different angulations and for 2 different LOCATOR attachments. Any significant differences were identified with the Tukey HSD test (alpha=.05). The percentage decrease in the dislodgement force was also calculated. RESULTS: A significant 3-way interaction was found for the LOCATOR type, implant angle, and time (P<.001). LOCATOR type made a difference for only parallel and 60 degree-divergent implants before cyclic dislodgement (P</=.022). After cyclic dislodgement, a significant effect of the LOCATOR type on dislodgement force was found for only parallel implants (P=.034). In both LOCATOR systems, the dislodgement force was different (P<.001) among different implant angulations, except for parallel to 30-degree comparison, before and after cyclic dislodgement. For both LL and R-Tx, significant differences (P</=.022) were found between before and after cyclic dislodgement for all angulations except LL in parallel (P=.214). CONCLUSIONS: When implants were parallel, initially, the dislodgement force of R-Tx was higher than that of LL; however, the forces were similar after cyclic dislodgement. When implants were divergent by 30 degrees, there were no differences between the dislodgement forces of the LOCATOR systems before and after cyclic dislodgement. When implants were divergent by 60 degrees, initially, the dislodgement force of LL was higher than that of R-Tx; however, the forces were similar after cyclic dislodgement. Before and after cyclic dislodgement, in each system, dislodgement forces were greater when implants were divergent by 60 degrees than when parallel and 30 degrees. After cyclic dislodgement, dislodgement forces decreased for both systems, except for LL when the implants were parallel.