Does the metal in the mouth affect nuclear magnetic resonance imaging?

Recently, a man in his 60s went to the provincial dental hospital and requested doctors to remove numerous metal dentures in his mouth because he had a cerebral infarction and needed an MRI examination. Considering that the artifacts generated by metal in the oral cavity may affect the accuracy of the diagnosis, the doctor suggests that he remove all of them before conducting an examination.
Magnetic resonance imaging has the advantages of high contrast, no bone artifacts, and arbitrary orientation tomography, playing an irreplaceable role in head and neck surgery, neurosurgery, and oral and maxillofacial surgery. However, metal restorations in the oral cavity can affect areas such as the brain, neck, face, and inner ear during magnetic resonance imaging. Therefore, it is necessary to understand the extent to which various metal repair materials have an impact on nuclear magnetic resonance.
Technically speaking, the artifacts caused by metal materials can be divided into ferromagnetic metal artifacts and non ferromagnetic metal artifacts. The size of the artifacts generated is related to the magnetic susceptibility and magnetic field strength of the metal material. The higher the magnetic susceptibility and magnetic field strength, the greater the artifacts generated.
Research has shown that in the same imaging sequence, gold alloy has the smallest impact, followed by soft cobalt chromium alloy, and hard cobalt chromium alloy has the largest impact. Under different imaging sequences, the artifacts generated by the same metal are also different. When it is recommended that only metal crowns can be used for oral fixed restoration, precious metal crowns are preferred. When cobalt chromium alloy crowns must be selected, it is necessary for the MRI examination physician to choose a reasonable imaging sequence (choose spin echo sequence and avoid using planar echo sequence).
In addition, the classic dental filling material - amalgam is also an alloy material. Although its impact on magnetic resonance imaging is relatively small and within an acceptable range, in order to minimize or avoid the formation of artifacts, it is still recommended that patients choose non-metallic materials such as composite resin for dental restoration.
Some people also think that dental implants are also made of metal, will it have an impact on magnetic resonance imaging? The answer is, no. Because the vast majority of dental implants are made of pure titanium, which has excellent physical and chemical properties. Titanium metal is non magnetic, and pure titanium dentures will not be magnetized in a magnetic field, so it will not affect the head MRI examination.
In summary, gold, platinum alloys, silver, and amalgam alloys have minimal impact on nuclear magnetic resonance; Pure titanium also produces relatively small artifacts, while cobalt chromium alloy and nickel chromium alloy have a significant impact on nuclear magnetic resonance. At the same time, the position and size of metal restorations in the mouth also have an impact on the differences in MRI artifacts. The size of the artifact is twice the mesial diameter of the metal crown bridge and four times its buccal lingual diameter.
Therefore, it is recommended to prioritize all ceramic restorations when using fixed oral restorations. When metal crowns and bridges are necessary, priority should be given to precious metals (such as gold alloys and platinum alloys), followed by pure titanium metals, followed by titanium containing alloys, and finally cobalt chromium and nickel chromium alloys. Even if choosing precious metals, it is still advisable to use individual single crowns to avoid multiple unit crown bridge repairs.