RETENTION OF ERA DIRECT OVERDENTURE ATTACHMENTS BEFORE AND AFTER FATIGUE LOADING

This in vitro study investigated the retention of the four different c olor-coded ERA attachments prior to and after various levels of fatigu e loading (at baseline, at 500 cycles, and after every 500 cycles up t o 5,500 cycles). Samples were placed in the Instron testing machine fo r determination of initial retentive values and then cycled in a speci ally designed fatigue machine and retested. The results of this study demonstrated that although there are four different retentive elements supplied by the manufacturer of the ERA system, there were only two s ignificantly different groups: (1) the while attachments and (2) the o range, blue, and gray attachments (P < .05). After 500 cycles, there w as a loss in retention of 60% for the white, 60% for the orange, 56% f or the blue, and 54% for the gray. After 1,500 cycles there was no dif ference in retentive values for any of the four colored attachments (P < .05). Microscopic examination of worn specimens supported the findi ngs of the fatigue testing.