Breakaway forces of flat and domed surfaced Magfit implant magnet attachments.

The aim of this in vitro study was to compare the resistance to separation (breakaway force) of flat (Magfit-IP-BF) and domed (Magfit-IP-BD) implant magnet attachments subjected to non-axial forces. The separating forces were applied by an Instron Universal Testing Instrument to single magnet attachments at angles of 0 degrees, 2 degrees, 5 degrees 10 degrees, and 20 degrees from the axial line of the components (angle of pull) and at crosshead speeds of 0.5 mn/min and 5 degrees mm/min. The breakaway forces were significantly (p < 0.0001) inversely related to the angle of pull for both flat magnets and for domed magnets. At the slow crosshead speed, the breakaway forces recorded for the domed magnets were significantly greater than those recorded for the flat magnets for angles of pull greater than 5 degrees. At the faster crosshead speed, the breakaway forces recorded for the domed magnets were significantly greater than those recorded for the flat magnets for angles of pull greater than 2 degrees. This apparent superiority of domed magnets under non-axially directed separating forces could influence the choice of magnet attachment for implant overdentures as intraoral displacing forces are multidirectional. Domed magnets may also be advantageous where implants are not parallel.