[Alteration of flux density of highly coercive SmCo magnets used in prosthodontics and epithetics in 1.5 T and 3 T MRI]

The opposing field stability of highly coercive dental magnets in external magnetic fields of 1.5 and 3 T magnetic resonance imaging (MRI) was investigated. It was further assessed if remagnetizing can reverse the flux density in the magnets.Using an adjustable fixture, 20 SmCo magnets were exposed and 6 positions of prosthodontics and epithetics were simulated: P : in the lower jaw parallel to the main field BWith 1.5 T clinically relevant loss of flux density between 7% and 10% occurred only in the angled positions Ad and Av and the external position AHighly coercive SmCo magnets can remain in situ during a 1.5 T MRI scan unless the resulting artifacts are diagnostically relevant. Exposure to the 3 T main field in antiparallel position may result in a complete loss of the adhesive force. In this case the magnets should be remagnetized by the manufacturer. Inclination or reclination of the head reinforces the effect of the main field.