Artifact size cannot be predicted merely from the designation "steel". Nor did the crystalline structure of the baseline material from which a steel device had been produced have major implications for artifact size. Relevant, however, was the magnetic permeability (or susceptibility) of the final products, which is not disclosed by the manufacturers, and it cannot be measured on fixed intraoral appliances. Furthermore, the present investigation reveals that some steel devices can remain in situ without triggering adverse consequences.

Ferromagnetic materials used in dentistry are not intraorally standardized. To ensure, that the area of interest is not affected by the described artifacts, the maximum extent of the signal loss area should be assumed: a radius of up to 7 cm in 1.5 and 3.0 T MRI by T1 and T2 sequences, and a radius of up to 10 cm in T2* sequences. To decide whether magnet attachments have to be removed before MR imaging, physicians should consider both the intact retention of the keepers and the safety distance between the ferromagnetic objects and the area of interest.

As a precaution, the worst-case scenario, i. e. an antiparallel orientation, should be assumed when using a duo-magnet system. If an MRI can be postponed, the general dentist should remove implant-borne magnets. If there is a vital indication, irreversible damage to the magnets is acceptable in consultation with the patient since the replacement costs are irrelevant given the underlying disease.

No abstract