[Medical Q&A] Can patients with dentures undergo MRI examinations?

Planner: Chinese Medical Association

Reviewer: Wang Xuan, deputy chief physician, Peking Union Medical College Hospital

Magnetic resonance imaging (MRI) uses a strong magnetic field and radio frequency waves to excite hydrogen atoms in the human body, thereby generating signals for imaging. In this process, any substance containing metal may interfere with the magnetic field, thereby affecting the image quality, and the closer the metal substance is to the magnetic field, the greater the impact. Therefore, for patients wearing dentures, the specific part of the examination and the material of the denture determine whether the patient can undergo an MRI examination.

For chest and abdominal examinations, all types of dentures generally have little effect; for examinations of limb joints, all types of dentures have basically no effect. Because the oral cavity is relatively far away from these structures, the artifacts produced by dentures in MRI examinations usually do not directly interfere with the imaging area. Examinations of the head and neck are greatly affected by dentures. For removable dentures, if they are made of metal, they can be removed before the MRI examination to avoid interference with the examination results. For fixed metal dentures, since they cannot be removed, they may have a certain impact on the MRI examination.

Traditional metal dentures, such as cobalt-chromium alloy and nickel-chromium alloy, will produce large artifacts during MRI examinations. This is because metal will interfere with the uniformity of the magnetic field of MRI, causing deformation, distortion, signal loss, etc. in the image, which seriously affects the accuracy of the examination results and may prevent doctors from clearly observing the area around the dentures, making it difficult to make an accurate diagnosis. In rare cases, metal dentures may also shift and cause damage during MRI examinations due to the attraction of the magnetic field. For the above reasons, it is generally not recommended for patients wearing fixed metal dentures to undergo MRI examinations. If it is necessary, it is recommended to remove the metal dentures before the examination. Metal porcelain teeth contain metal base crowns inside, which will also produce artifacts in MRI examinations, but the degree of artifacts may be slightly smaller than that of pure metal dentures, but it may still have a significant impact on the examination results. If the patient's dentures are made of materials that do not contain metal, such as all-ceramic teeth or non-metallic porcelain teeth, then these materials will not interfere in the magnetic field, and the patient can usually undergo MRI examinations normally.