Retentive characteristics of different magnetic systems for dental applications.

Six magnet-keeper systems were tested to determine the relationship between an air gap and the resulting breakaway force. The maximum retention was obtained when the magnet and keeper were in apposition. However, as the air gap increased in 0.1 mm increments, the breakaway force diminished rapidly initially and, then began to taper off at 0.2 to 0.3 mm. Ideally, the preferred placement of the magnet into the denture is with a carefully controlled system to provide an air gap. Then the magnet is attached with a minimal amount of autopolymerizing acrylic resin.