Magnetic displacement force and torque on dental keepers in the static magnetic field of an MR scanner

Results: The maximum magnetically induced displacement forces were calculated to be 10.3 10 2 N at 1.5 T and 13.9 10 2 N at 3.0 T on the cover surface. The maximum torques exerted on the keeper (4 mm in diameter) were 0.83 N 4 mm at 1.5 T and 0.85 N 4 mm at 3.0 T. These forces were considerably higher than the gravitational force (7.7 10 4 N) of the keeper but considerably lower than the keeper-root cap proper adhesive force. The keepers’ magnetic flux density remained less than that of the Earth.