THE SPECIALIST

Should there be a concern for patients who are to undergo a MRI scan and who have a separated file near the apex embedded in gutta percha? Assume the file is magnetically attracted.

By Dr. Barry H. Korzen

As careful as we are, instrument separation occurs and the consequences have to be dealt with. When the instrument fragment cannot be removed we have both a legal and moral obligation to inform the patient. Not only for the impact this may have on the prognosis of the endodontic treatment, but also on any other medical implications that might surface in the future. A case in point is the question asked concerning a MRI scan.

The question was passed on to the world’s expert on MRI safety, Emanuel Kanal, MD, FACR, FISMRM, AANG. Dr. Kanal is Director, Magnetic Resonance Services and Professor of Radiology and Neuroradiology in the Department of Radiology, University of Pittsburgh Medical Center.

Here is Dr. Kanal’s reply:

Are we certain that this is indeed ferromagnetic?  It might be possible to test whether or not it is ferromagnetic by bringing the mandible up against a hand held ferromagnetic detector (Mednovus Corporation) if one is available.  If not, if we do not know for certain whether or not it is ferromagnetic, one might consider walking the patient very slowly to the MR scanner, slowly laying them down onto the table while still at some distance from the MR scanner, then slowly advancing the patient into the bore to see if they experience any sensation.  If it would be my patient I would first review the x-rays to determine the precise position and even orientation of the long axis of the metal fragment so that I might be able to prospectively asses the likelihood – or lack thereof – of significant torque.  Also be aware that IF it is ferromagnetic and 5 mm or so in size it will throw off a rather substantial field distortion that for some sequences would be able to interfere with diagnostic image content and produce an artifact that could be 15 or 20 cm in diameter on a 1.5T or especially 3T MRI system (assuming of course that we would be performing an MR imaging examination of the head or the region in/around the retained metallic fragment).

When asked if he would consider having the tooth extracted prior to the MRI, Dr. Kanal answered:

I would not personally jump at extracting an otherwise healthy viable tooth, as this has its own risks and I do not believe that this should be the first step tried before a requested MRI examination.

Dr. Kanal asked that we publish his contact e-mail address, ekanal@pitt.edu, if anyone has any questions and wish to clarify or discuss this with him further.  He said “I’d rather be inundated with questions than have someone misinterpret or misunderstand my intent and inadvertently harm someone.”

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