The retentive and morphologic changes of overdenture attachments were evaluated independently after repeated insertion and sinusoidal loading on implant abutments. Stud and magnetic attachments were embedded in overdenture housings (n = 5). The overdentures were subjected to either repeated insertion and removal for 5,400 cycles or sinusoidal cyclic loading for 100,000 cycles. A 67.8% decrease in retentive force was observed after 100,000 loading cycles (P .05), and a 73.9% decrease of retentive force occurred after 5,400 insertion-removal cycles (P .05). Stud attachments showed more loss of retention and physical deterioration than magnetic attachments tested under identical conditions.