Dangers during MRI Examination and Impact on MR Images for Patients with Restorative Prostheses

<p>In Magnetic resonance imaging （MRI）, the dental region and oral cavity area is a region where image deterioration is observed due to metal artifacts associated with restorative prostheses.</p><p>A metal artifact is one of the magnetic susceptibility artifacts in MRI.</p><p>MRI images of patients wearing metal objects, especially ferromagnetic materials such as those containing iron, cobalt, and nickel, suffer from significant distortion. The effects of magnetic metals are not limited to image distortion; the heat generated by the metal itself and changes in the position of the magnetic material due to magnetic force pose problems for the human body.</p><p>On the other hand, among metals, non-magnetic metals（titanium, gold, silver, palladium, etc.） that do not become magnetized even when exposed to a magnetic field are considered safe metals for MRI examinations.</p><p>All dental magnetic metals, including magnetic attachments, vary in magnetic content and nature, but MRI distortion from the base of the skull to the pharyngeal region is basically observed due to magnetic metals. Regarding the problem of metal heat generation, experiments and literature indicate that there is almost no possibility of burning the oral mucosa with magnetic dental metals. However, another problem is that the keeper deviates from the abutment tooth due to deterioration of the resin cement that fixes the magnetic material such as the keeper, which becomes a problem in long-term use. When a magnetic material is adhered, it is desirable to re-adhere it in about 3-4 years considering deterioration over time.</p><p>Increasing the static magnetic field strength of clinical MR equipment from 1.5 T （Tesla） to 3.0 T does not change the above observations and knowledge.</p>