Often in the clinical encounter with patients consulting after the porcelain teeth if you are sick to carry out magnetic resonance imaging (hereinafter referred to as MRI) examination whether the porcelain teeth need to be removed, will affect the results of the examination, can not do, there are dangers, etc., in fact, really ask why? Most dentists are basically the same as the others. Do porcelain teeth really can not do MRI examination? Is there any scientific basis? Now discuss the relevant information. (A) magnetic resonance (MRI) examination principle: MRI technology is the application of nuclear magnetic resonance in the field of medicine, because the human body contains very rich water, different tissues, water content varies, if you can detect the distribution of these water information, you can draw a more complete picture of the internal structure of the human body, MRI technology is through the identification of water molecules in the hydrogen atom signal MRI is a technique that detects the internal structure of the human body by identifying the distribution of hydrogen atoms in water molecules to infer the distribution of water molecules in the human body. Unlike MRI spectroscopy, which is used to identify molecular structures, MRI changes the strength of the applied magnetic field rather than the frequency of the RF field. Nuclear magnetic resonance (MRI) examination machine equipment is in the direction perpendicular to the main magnetic field will provide two mutually perpendicular gradient magnetic field, so that the distribution of magnetic field in the human body will change with the change of spatial location, each location will have a magnetic field of different intensity and direction, so that the hydrogen atoms located in different parts of the body will respond to different RF field signals, by recording this response, and through computer computing and processing, it is possible to obtain information about the distribution of water molecules in space and thus obtain images of the internal structure of the human body. (A. Since there is a very strong magnetic field in the MRI machine and the MRI examination room, it is strictly forbidden to perform MRI examination for people with pacemakers, metal clips or metal stents after vascular surgery, or other metal stents for coronary artery, esophagus, prostate, or bile duct surgery, otherwise, the metal will be attracted by the strong magnetic field and move. Otherwise, the metal will be attracted by the strong magnetic field and may produce serious consequences that may be life-threatening (note the description here). B, the body can not remove other metal foreign bodies, such as metal internal fixation, artificial joints, metal dentures, stents, silver clips, shrapnel, and other metal remains, for the examination of the relative contraindication, must be examined, should be closely observed, to prevent the examination of metal in the strong magnetic field movement and damage to the adjacent large blood vessels and important tissue, resulting in serious consequences, metal contraceptive ring and movable metal dentures must be removed before The examination should be carried out after the removal of metal contraceptive rings and movable metal dentures. In addition, and because of the strong magnetic field, metal objects may be sucked into the MRI machine, thus causing damage to the very expensive MRI machine; from the above paragraph can be seen, we do the regular porcelain teeth or metal crowns and bridges can simply do not appear above the accidental situation, the magnetic field is not so strong as to attract porcelain crowns and bridges and move, or the loss of large blood vessels and important tissues around it! The magnetic field is so strong to attract the fixed crown bridge to fall off? C, on the issue of the impact of MRI (this is the focus): the scientific description is this, sometimes, the metal iron ions left in the body may affect the image quality, and even affect the correct diagnosis, because the examination of the metal iron ions may affect the uniformity of the magnetic field, resulting in image interference, the formation of artifacts, not conducive to the display of lesions. Then we analyze the text again, we make porcelain crowns, the most common metal is mainly medical nickel-chromium alloy, which is mainly composed of nickel, chromium and a small amount of other metal elements harmless to humans, as for cobalt-chromium alloy, which the content of metal iron ions is how much, basically one percent to zero point a few only! We are interested to check the corresponding data! In fact, you can not use the concept of iron ions to locate, and the word ferromagnetic material is more appropriate, ferromagnetic materials in dentistry mainly include “iron, nickel, chromium” these three materials, and more high-end porcelain teeth or metal crowns, such as pure titanium porcelain, gold alloy and other precious metal porcelain teeth or dental implants, the situation is less worry! The patient who has titanium metal internal fixation in his body is safe for MRI examination because titanium metal is not attracted by magnetic field and will not move in the magnetic field, and the metals such as gold, silver and titanium will not interfere meaningfully with the MRI image. From the above information, I think the only explanation for saying that porcelain teeth or metal teeth can not do MRI can only be afraid of “artifacts”, in fact, the reality of the situation is that MRI and dentists may be a muddled understanding of each other, because MRI operators do not know enough about the material of porcelain teeth, dentists do not know enough about the principles of MRI, remove seems to be good for everyone, MRI operators The MRI operator must think that the removal at least for his operation is not bad, the dentist thinks that the removal may be insurance, at least for him there is no harm, and perhaps a big business can be done again. So how much do these ferromagnetic materials (iron, nickel, chromium) affect MRI imaging? From the data reviewed: the interference signal area is oval, consistent with the long axis of the fixed bridge or single crown, and its maximum impact range is about two times the near and far middle diameter of the fixed bridge or crown, and four times the buccolingual diameter, even if this data is accurate, but how much impact on the area we really want to examine? Even if this data is accurate, how much effect does it have on the area we really want to examine? The artifacts are limited to the lower 1/3 of the face at most, which basically has no effect on the cervical spine, and MRI is generally more advantageous for those areas than panoramic film or CT? In addition, I remember that Professor Ma Xuchen said that the impact of porcelain teeth on MRI in the mouth can be eliminated by adjusting the scan tomography of MRI. So my personal view is: 1, wearing a nickel-chromium alloy restorations can safely accept the head and neck MRI examination; 2, nickel-chromium alloy restorations so that the adjacent tissue MRI has an impact, but the impact on the anatomical image is very small, the impact on the functional image is slightly larger; 3, precious metal porcelain and pure titanium porcelain, implants basically no impact.