Retention of prefabricated attachments for implant stabilized overdentures in the edentulous mandible: An in vitro study

Statement of problem. Bar and stud attachments are widely used to stabilize overdentures on implants in the mandible. There is strong evidence that retention of the attachment is an important factor for a patient's satisfaction. Purpose. This study describes retentive forces and wear of commercially available attachments of 4 implant systems (3I, IMZ, Nobel Biocare, ITI Straumann) and 2 magnets (Steco). Methods. Forces while removing the keyway portion of an attachment in its path of insertion were measured with a platform load cell. A total of 15,000 removals were performed to simulate fatigue. Results. Retentive forces ranged between 5 and 85 N. The fatigue test revealed an initial increase of forces with some attachments. After 15,000 cycles, most of the attachments showed little loss of retention compared with the initial retentive: forces. It is suggested that conventional fatigue tests with application of axial loads do not simulate clinical fatigue adequately.