Dr. Hall,
Is the metal used in a Maryland bridge M.R.I.safe?
– Kevin from the U.K.

Kevin,
You’re referring to the use of metals with magnetic properties that should be avoided around magnetic resonance imaging machines. There is an excellent article that discusses this issue on a blog called the MRI Metal Detector Blog, and I would refer anyone with more questions about this to that blog. There is another piece from the National Institutes of Health about the interactions between MRI and dental materials, but they offer no definitive conclusions—they only bring up the problem.

The metal in a Maryland Bridge is generally a non-precious dental alloy. It has to either have some beryllium in it or be tin plated. Neither of those metals has magnetic properties. But often the metal will have cobalt and/or nickel also, possibly a lot of cobalt or nickel, and both these metals do have magnetic properties. If that is the case, would the pull of the MRI machine be enough to dislodge the bridge? I doubt it, but I confess that I don’t know enough about the MRI machines to say for certain. I would refer the question to an MRI technician. To function in the mouth, a Maryland Bridge has to be designed and bonded so as to resist chewing forces, which are very heavy forces. If chewing won’t dislodge it, I doubt that an MRI machine would be able to. But Maryland Bridges can sometimes be done without proper designing to resist dislodging forces, which is why patients have problems with them falling out from time to time.

There are other types of dental work that also use these alloys. Crowns and bridges, as well as removable partial denture frameworks, can be made out of non-precious alloys (also called base metal alloys). Crowns and bridges, again, should be cemented very securely so that they resist chewing forces, and I have a hard time believing that a conventional crown or bridge could have an issue with MRI forces. A removable partial denture, however, is not fastened very securely, and if there is any cobalt or iron in the framework, my recommendation would be to remove the prosthesis before having an MRI.

– Dr. Hall

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