3-T MRI safety assessments of magnetic dental attachments and castable magnetic alloys

Abstract

The tested devices showed minimal radiofrequency (RF)-induced heating in a 3-T MR environment, but the cast magnetic alloy coping showed a magnetically induced deflection force and torque approximately eight times that of the keepers. For safety, magnetic dental attachments should be inspected before and after MRI and large prostheses containing cast magnetic alloy should be removed. Although magnetic dental attachments may pose no great risk of RF-induced heating or magnetically induced torque during 3-T MRI, their magnetically induced deflection forces tended to exceed acceptable limits. Therefore, the inspection of such devices before and after MRI is important for patient safety.

Colorless polyimides derived from 1S,2S,4R,5R-cyclohexanetetracarboxylic dianhydride, self-orientation behavior during solution casting, and their optoelectronic applications

“…This motivated us to develop a novel CF 3 -containing rigid diamine [52]. The combination of this diamine with H 0 -PMDA led to a solution-processable colorless PI with a further decreased CTE (16 ppm K À1 ).…”

Unwanted effects due to interactions between dental materials and magnetic resonance imaging: a review of the literature

“…The potential unwanted effects caused by the interaction of MRI and dental materials fall into 3 broad categories ( Table 1 ) [ 20 21 22 23 ].…”

“…The magnetic field is strong enough to pull heavy objects towards the scanner at a very high velocity (known as the projectile effect) [ 38 ]. The translational attraction (dependent on magnetic field strength and the object's mass, shape, and magnetic susceptibility) and resultant torque may cause the movement or dislodgment of ferromagnetic implants, resulting in uncomfortable sensation or injury to the patient [ 22 39 40 ].…”

“…According to testing standards (ASTM F2052-06) of magnetically-induced deflection, if the device under testing is deflected by < 45°, the risk induced by this deflection force is no greater than that imposed by normal daily activity in the earth's gravitational field [ 41 ]. Hasegawa et al [ 22 ] found that the deflection angles were > 90° with deflection forces of 0.03–0.3 N for magnetic dental attachments with castable alloys (components of removable partial denture prostheses) during 3 T MRI. The authors concluded that magnetic dental attachments may cause patient discomfort, but the retention force of dental luting cement (48–150 N) is strong enough to prevent prosthesis dislodgment.…”

Artifact on MR imaging by a dental magnetic attachment keeper: Preliminary study on a new keeper removable phantom

“…Dental magnetic attachments with satisfactory retentive force and stability are now commercially available for dental treatment . A dental magnetic attachment is made of a magnetic assembly and a keeper.…”