The change of retentive force of three types of Locator inserts when the implant analogue was positioned perpendicular to horizontal, 5 degrees and 10 degrees to perpendicular after 4,200 cycles in vitro was measured using an EnduraTech fatigue testing machine lubricated with artificial saliva. The more rapid decrease in retention occurred up to three months and stabilized after one year of simulated use. The Locator inserts provided more retention when the analogue was placed at 5 degrees to perpendicular compared to 0 degrees and 10 degrees after 9 months of simulated clinical use. After 2 years of simulated clinical use, there was a reduction in retention for all the three inserts of between 70% and 80%.