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Context Although in recent times more research has been done on interactions of metallic dental objects in magnetic resonance imaging (MRI), radiologists are often uncertain whether the objects should be removed or can be retained prior to an impending examination. On the one hand, they want to avoid unnecessary material removal which is associated with costs and potential damage of the dental object. On the other hand, they fear material-induced susceptibility artefacts will impair the diagnostic workup so that examinations will have to be repeated. The lack of information complicates adequate decision making for radiologists. Aim The aim of this survey was to evaluate the information that is currently available to radiologists regarding orthodontic appliances of the head and neck region in the MRI and determine how to handle these situations in a radiologist's every day routine. Therefore, this study can reveal the need for further research. Materials and methods The questionnaire was published in the 9/2017 issue of the journal Der Radiologe and sent as an electronic version by the BDR (Professional Association of German Radiologists) to their approximately 1800 members. In addition, the radiological institutes of 55 German university and maximum care clinics were contacted. Results In all, 74 evaluable responses were received within a period of 16 weeks, representing a response rate of 3.7%. Altogether, the participants rate the risks of a detachment or heating of orthodontic appliances as too high. The interviewed radiologists categorize the available data as insufficient and they almost unanimously (97.3%) demand a declaration requirement for the manufacturers. There is a clear need for further education (78.3%). Intraoral measurement of the magnetic permeability is considered as a useful tool to determine possible interactions with the MRI by 40.5%.

Es wurde die Gegenfeldfestigkeit hoch koerzitiver Dentalmagnete in der 1,5- und 3‑T-Magnetresonantomographie (MRT) untersucht und gepruft, ob dadurch geschadigte Magnete durch Remagnetisieren in den alten Zustand versetzbar sind. Es wurden in einer justierbaren Halterung je 20 SmCo-Magnete in sechs simulierten Positionen der zahnarztlichen Prothetik/Epithetik exponiert: P : im Unterkiefer, parallel zum Hauptfeld B0, A: im Oberkiefer, antiparallel zu B0, Ad: antiparallel mit um 45° rekliniertem Kopf, Av: antiparallel um 45° inkliniert, G: Glabella, 90° zu B0, M: Mastoid, 90° zu B0. Im Ausenfeld vor dem Portal wurden die parallele (Pex), antiparallele (Aex), Glabella (Gex) und Mastoid (Mex) -Positionen erneut gepruft. Nach jeder Exposition wurden die Magnete remagnetisiert. Als Aquivalent der Magnetkraft wurde die relative Anderung der Flussdichte bestimmt. Bei 1,5 T kam es nur in den abgewinkelten Positionen Ad und Av und in der Ausenposition Aex zu klinisch relevanten Verlusten der Flussdichte zwischen 7 % und 10 %. Das starke Gegenfeld von 3 T erzeugte bei den antiparallelen Positionen A und Aex mit 72 % und 33 % sehr hohe Verluste. In den antiparallel inklinierten und reklinierten Positionen Ad und Av wurden die Magnete durch den Verlust von 96 % ihrer ursprunglichen Flussdichte nahezu entmagnetisiert. Unabhangig von ihrer Schadigung liesen sich alle Magnete anschliesend wieder vollstandig aufmagnetisieren. Sofern die induzierten Artefakte diagnostisch irrelevant sind, konnen hoher koerzitive SmCo-Magnete bei 1,5 T in situ bleiben. Im antiparallel wirkenden 3‑T-Hauptfeld kann ihre Haftkraft komplett verloren gehen. Dann sollten sie vom Hersteller remagnetisiert werden. Die In- oder Reklination des Kopfes verstarkt den Einfluss des Hauptfeldes.

Although in recent times more research has been done on interactions of metallic dental objects in magnetic resonance imaging (MRI), radiologists are often uncertain whether the objects should be removed or can be retained prior to an impending examination. On the one hand, they want to avoid unnecessary material removal which is associated with costs and potential damage of the dental object. On the other hand, they fear material-induced susceptibility artefacts will impair the diagnostic workup so that examinations will have to be repeated. The lack of information complicates adequate decision making for radiologists.The aim of this survey was to evaluate the information that is currently available to radiologists regarding orthodontic appliances of the head and neck region in the MRI and determine how to handle these situations in a radiologist's every day routine. Therefore, this study can reveal the need for further research.The questionnaire was published in the 9/2017 issue of the journal Der Radiologe and sent as an electronic version by the BDR (Professional Association of German Radiologists) to their approximately 1800 members. In addition, the radiological institutes of 55 German university and maximum care clinics were contacted.In all, 74 evaluable responses were received within a period of 16 weeks, representing a response rate of 3.7%. Altogether, the participants rate the risks of a detachment or heating of orthodontic appliances as too high. The interviewed radiologists categorize the available data as insufficient and they almost unanimously (97.3%) demand a declaration requirement for the manufacturers. There is a clear need for further education (78.3%). Intraoral measurement of the magnetic permeability is considered as a useful tool to determine possible interactions with the MRI by 40.5%.

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.