Standard dental fillings are safe inside an MRI scanner, and having them is not a reason to skip or delay a scan. The metals used in common restorations, whether amalgam (the silver-colored kind) or composite resin (tooth-colored), are not ferromagnetic in the way that, say, an iron plate would be. They do not get yanked by the magnet or cause dangerous heating. That said, the interaction between dental materials and MRI is not zero. Amalgam fillings produce a small but measurable release of mercury, metallic restorations can create image distortions, and larger dental hardware like bridges or orthodontic wires behaves differently than a simple filling. The story gets more interesting as MRI field strengths climb higher.
Why Dental Metal Reacts to MRI at All
An MRI machine uses an extremely strong static magnetic field, rapidly switching magnetic gradients, and radiofrequency energy. Anything metallic inside that field can, in principle, experience three types of interaction: it can be physically pulled or twisted, it can absorb radiofrequency energy and heat up, and it can distort the magnetic field around it in ways that mess up the images. The severity of each effect depends on the type of metal, the size and shape of the object, and how strong the scanner is.
Dental amalgam is an alloy of mercury, silver, tin, and copper. These metals are weakly diamagnetic or paramagnetic, meaning the MRI’s magnet exerts only a trivial pull on them. Ferromagnetic materials like certain stainless steels and cobalt-chromium alloys respond much more strongly. That distinction is why a small amalgam filling sits quietly during a scan while a ferromagnetic surgical clip might not. In testing of magnetic dental alloys at 3-Tesla field strength, the greatest deflection force measured was only about a third of a Newton, roughly the weight of a few coins, and that was for a cast magnetic alloy coping designed to be attracted to a magnet, not a filling.1PubMed Central. 3-T MRI safety assessments of magnetic dental attachments and castable magnetic alloys Ordinary fillings generate far less force than that.
How Much Do Fillings Heat Up?
Radiofrequency energy is what makes MRI scans warm in general. Metallic objects can act as tiny antennas, concentrating that energy and heating up locally. For dental fillings, the effect is real but small. In tests using a 1.5-Tesla scanner, amalgam restorations showed temperature increases ranging from about 0.2°C to 0.7°C, with none exceeding 1°C. Titanium dental implants tested in the same study warmed by roughly 0.4°C on average. The differences between various amalgam brands were not statistically meaningful.2PubMed Central. Radiofrequency-Induced Heating of Amalgam Restorations and Dental Implants during 1.5T Magnetic Resonance Imaging
For context, your mouth temperature fluctuates by more than a degree when you drink a glass of water. A fraction-of-a-degree rise from an MRI scan is not something you would feel, and it is well within the range that oral tissues tolerate without any harm.
Larger metallic dental work is a different story. Testing at 3 Tesla found that bridges warmed by up to 1.8°C, a full-arch fixed prosthesis by about 1.6°C, and an orthodontic appliance by as much as 2.6°C.3PubMed Central. Radiofrequency heating of metallic dental devices during 3.0 T MRI These numbers are still within what safety guidelines consider acceptable, but they show why more metal means more heating. A single small filling and a mouthful of orthodontic brackets are not equivalent scenarios, even though both are cleared for scanning.
The Mercury Question With Amalgam Fillings
This is the concern that generates the most anxiety. Amalgam fillings contain mercury, and strong magnetic fields can, in theory, loosen the bond between mercury and the other metals in the alloy. Research confirms that something measurable does happen, though the clinical significance remains debated.
In one study, people who had amalgam fillings placed and then underwent MRI showed significantly higher urinary mercury levels compared to a control group that had the same fillings but no MRI. The MRI group’s mean urinary mercury rose from about 21 to 26 micrograms per liter, while the control group’s level actually dipped slightly. The difference remained statistically significant even 72 hours after the scan.4PubMed Central. High-Field MRI and Mercury Release from Dental Amalgam Fillings That is a real increase, but to put it in proportion, the levels stayed well below the thresholds associated with mercury toxicity symptoms. The World Health Organization considers urinary mercury above 50 micrograms per liter the point at which early health effects can begin, so even the post-MRI values in this study were about half that ceiling.
A separate lab study looking at mercury release into artificial saliva found that both the strength of the magnetic field and the radiofrequency power influenced how much mercury came out of amalgam fillings. The effect was dose-dependent: stronger fields released more mercury, and 7-Tesla scans released significantly more than 3-Tesla scans, which in turn released more than the control condition.5Journal of Dentistry. The effect of magnetic resonance imaging on mercury release from dental amalgam at 3T and 7T The 3-Tesla effect at standard power was modest, but at 7 Tesla, the jump was large enough to be noteworthy. The same research group also found that MRI exposure significantly increased microleakage of amalgam restorations, meaning the seal between the filling and the tooth became slightly less tight after scanning.6PubMed Central. The effect of 3 T MRI on microleakage of amalgam restorations
None of these findings have led to any regulatory body advising against MRI for patients with amalgam fillings. The amounts released during a single scan are small, and most people with amalgam fillings have had them for years, during which they have already been exposed to low-level mercury release through normal chewing and temperature changes. An occasional MRI adds a brief, modest spike on top of that background. Where this gets more interesting is with ultra-high-field scanners, which are discussed further below.
Do Fillings Ruin the Images?
Image artifacts from dental materials are the most common practical issue, though they rarely make a scan useless. When a metal object sits inside the MRI’s magnetic field, it creates its own local field distortion. Nearby hydrogen atoms, which are what MRI actually images, get thrown off their expected behavior. The result is a dark void, bright flare, or warped region on the image centered on where the metal sits.7PubMed Central. Artifacts In Magnetic Resonance Imaging and Computed Tomography Caused By Dental Materials
The practical impact depends on what part of the body is being scanned. If you are getting a brain MRI and you have a few amalgam fillings, the distortion sits in and around the mouth, jaw, and maxillary sinuses. A pediatric study found that preformed metal crowns (the stainless-steel caps commonly placed on children’s teeth) did create visible MRI distortions, but almost all of them stayed confined to the oral cavity and maxillary sinus and did not affect the brain areas that radiologists needed to read.8PubMed. Association between dental restorations and artefacts on head magnetic resonance images in paediatric patients Interestingly, children in that study who had only amalgam fillings or tooth-colored restorations did not show distortions at all. The artifacts came specifically from the metal crowns, and more crowns meant bigger artifacts.
For scans of the knee, spine, abdomen, or anything far from your mouth, dental fillings have no effect on image quality whatsoever. The artifact is extremely local. Even for head and neck scans, the distortion from a small filling is usually minor enough that the radiologist can read around it.
Composites, Ceramics, and Other Non-Metal Fillings
If your fillings are the tooth-colored composite resin type, or if you have ceramic inlays or onlays, you can stop worrying entirely. In a systematic comparison of 44 dental materials, all composites, all ceramics, and most temporary filling materials produced zero MRI artifacts.7PubMed Central. Artifacts In Magnetic Resonance Imaging and Computed Tomography Caused By Dental Materials These materials contain no significant metal content, so they do not interact with the magnetic field, do not heat up beyond what surrounding tissue does, and do not release anything.
Composite resin fillings have been the standard for front teeth for decades and are increasingly common in back teeth as well. If you are under 40, there is a good chance most or all of your fillings are composite. If you are unsure, your dentist’s office can tell you from your records. But even if you cannot find out, the answer does not change: go get your MRI.
Crowns, Bridges, and Orthodontic Hardware
The general rule is that the more metal in your mouth and the more ferromagnetic that metal is, the more interaction you will see. A single gold or porcelain-fused-to-metal crown behaves much like an amalgam filling: minimal force, modest heating, localized artifact. Full-arch bridges and orthodontic appliances involve more metal spread over a larger area, which amplifies all three effects.
Among the dental materials tested for MRI artifacts, metal alloys were the only group to produce distortions that projected far from the object itself. Two specific alloys, a cobalt-chromium and a gold-based alloy, created artifact regions that extended well beyond the immediate location of the material.7PubMed Central. Artifacts In Magnetic Resonance Imaging and Computed Tomography Caused By Dental Materials For someone with extensive bridgework or a fixed retainer who needs an MRI of the jaw, temporomandibular joint, or sinuses, the artifacts could genuinely interfere with diagnosis. In those cases, the radiologist may choose different imaging sequences, adjust the scan parameters, or in rare cases recommend an alternative imaging modality.
Orthodontic brackets and wires are safe in the scanner, but they produce the highest heating among dental devices tested and create substantial artifacts. If you are wearing braces and need a head MRI, the scan can almost always still be done, but the images of structures near the jaw will be degraded. Removable appliances like retainers or Invisalign trays should simply be taken out before scanning.
Artifact Reduction Techniques
Radiology departments have tools to mitigate metal artifacts when they interfere with diagnosis. Metal artifact reduction sequences, commonly known as MARS, are specialized MRI protocols that adjust how the scanner collects and processes data to minimize distortion around metallic objects. In testing on skulls with titanium and titanium-zirconium dental implants, MARS significantly reduced artifact size.9Iranian Journal of Radiology. Optimizing MRI Protocols with Metal Artifact Reduction Sequences in Dental Implants: An In Vitro Study on Dry Human Skull at 1.5 T One interesting wrinkle: the same study found that MARS actually increased artifacts around zirconia implants, which are non-metallic ceramic materials that normally produce little distortion on their own. The lesson is that artifact reduction is not one-size-fits-all; the approach depends on what is in the patient’s mouth.
Endodontic materials, the ones placed inside root canals, also contribute to artifacts differently depending on the MRI sequence used. Some root canal sealers and posts contain metallic particles that create larger distortions than surface fillings, particularly in anatomical imaging sequences.10Oral Surgery, Oral Medicine, Oral Pathology and Oral Radiology. Influence of dental materials on artifacts and image quality in dental-dedicated MRI If you have had a root canal and need an MRI of the jaw or face, mentioning it to the MRI technologist helps them choose the best protocol.
That Metallic Taste People Report
Some people report tasting metal during an MRI, and it is natural to assume this is caused by their fillings somehow reacting to the scanner. The reality is more mundane. Research on metallic taste perception in MRI found that the sensation is triggered by rapidly changing magnetic fields stimulating nerves or inducing tiny electrical currents on the tongue. Crucially, having dental fillings is not required to experience it. About half of test subjects perceived a metallic taste when moving their head in a strong field that changed at a rate of roughly 2.3 Tesla per second, regardless of whether they had fillings.11PubMed. Thresholds for perceiving metallic taste at high magnetic field
So if you taste metal during your scan, it is not your fillings leaching into your mouth in real time. It is your nervous system responding to the magnetic field. The sensation is harmless and goes away as soon as you leave the scanner room.
Ultra-High-Field MRI and What Changes
Most clinical MRI scanners run at 1.5 or 3 Tesla. A growing number of research centers use 7-Tesla scanners, which produce dramatically sharper images of brain structures, cartilage, and other tissues. As field strength goes up, every interaction between metal and the scanner gets amplified.
For amalgam fillings specifically, the mercury release story changes at 7 Tesla. Lab measurements found that mercury concentrations in artificial saliva were roughly four times higher after 7-Tesla exposure compared to 1.5 Tesla or no exposure at all. At 3 Tesla with high radiofrequency power, mercury release was also significantly elevated above controls, though less dramatically than at 7 Tesla.5Journal of Dentistry. The effect of magnetic resonance imaging on mercury release from dental amalgam at 3T and 7T This matters because 7-Tesla systems are becoming more common for neuroimaging research, and research subjects sometimes undergo repeated scans over weeks or months. A single scan’s mercury release is unlikely to cause harm, but repeated ultra-high-field exposures in someone with multiple large amalgam fillings is a scenario that researchers are still evaluating.
Artifacts are also worse at higher field strengths. The same filling that causes a small, ignorable dark spot at 1.5 Tesla can create a much larger void at 3 Tesla and an even bigger one at 7 Tesla. For routine clinical brain scans at 1.5 or 3 Tesla, this is manageable. For 7-Tesla research imaging of structures near the mouth, such as the hippocampus or temporal lobes, dental artifacts can be a genuine limitation.
What to Tell the MRI Staff
Before any MRI, you fill out a screening questionnaire. It asks about metallic implants, pacemakers, surgical hardware, and similar items. Standard dental fillings, whether amalgam or composite, do not need to be flagged as a concern. They are considered MRI-safe by every major radiology safety guideline. You do not need to have them removed before a scan, and no scan should be refused or delayed because of them.
What is worth mentioning: extensive bridgework, orthodontic appliances, magnetic dental attachments used in some overdentures, or any dental work you know involves cobalt-chromium or nickel-chromium alloys. These may not prevent the scan, but they help the technologist choose the right sequences and anticipate where image artifacts will appear. If you have a removable dental prosthesis or retainer, take it out. If it is permanently cemented, leave it alone and let the MRI team handle the rest.
The bottom line for anyone anxiously searching this question before a scheduled scan is straightforward: your fillings will not fly out of your teeth, will not burn your gums, and will not poison you. They might create a small blind spot on the images if the scan is close to your jaw, but your radiologist deals with that routinely. Go to your appointment.
Dental MRI as an Emerging Imaging Tool
An ironic twist in this story is that MRI is increasingly being explored as an alternative to dental X-rays, not just a modality that fillings might interfere with. Dental-dedicated MRI systems are being developed to image teeth, periodontal structures, and jaw pathology without ionizing radiation. These systems face a unique challenge: the very patients who need dental imaging are the ones most likely to have metal in their mouths from previous dental work.
Research into how different dental materials affect image quality on these specialized dental MRI systems shows that the type of material matters more than on a standard body scanner, because the region of interest is right next to the metal. Endodontic materials placed inside root canals tend to cause larger distortions on dental MRI than surface fillings do, since they sit deeper within the tooth structure and closer to the tissues being imaged.10Oral Surgery, Oral Medicine, Oral Pathology and Oral Radiology. Influence of dental materials on artifacts and image quality in dental-dedicated MRI Artifact reduction sequences help for metallic implants but can paradoxically worsen image quality around non-metallic materials like zirconia.9Iranian Journal of Radiology. Optimizing MRI Protocols with Metal Artifact Reduction Sequences in Dental Implants: An In Vitro Study on Dry Human Skull at 1.5 T As dental MRI matures, the relationship between restorative materials and magnetic resonance imaging will become a two-way design problem, with future filling materials potentially being optimized not just for chewing forces and aesthetics but for MRI compatibility as well.