Imagine you’ve been scheduled by your physician to undergo an MRI test. You are likely to receive and be expected to fill out a questionnaire that asks if you have any metal objects, implants, or fragments on or in your body. Oddly enough, it is unlikely you will be asked if you have any metal dental fillings. Why? Before answering this question, let’s discuss first what MRI stands for, and what it does.
What is an MRI?
MRI stands for Magnetic Resonance Imaging. This name replaced an older name, NMR, which stood for Nuclear Magnetic Resonance. There was nothing inaccurate about this descriptive name, so why was it replaced? Doubtless it was due to the unfounded public concern that nuclear radiation is employed in NMR testing. In reality, the patient so tested never receives X-rays or other harmful ionizing radiation. As the website RadiologyInfo.org tells us, “MR imaging uses a powerful magnetic field, radio frequency pulses and a computer to produce detailed pictures of organs, soft tissues, bone and virtually all other internal body structures.” Thus it is a tool for your doctor to see what is going on inside your body’s routinely inaccessible areas.
Preparing for the Test
The word magnetic in Magnetic Resonance Imaging suggests metallic objects could interfere with testing. Such is the case. Thus, before entering the machine the patient will be asked to empty his pockets-perhaps into a temporary locker. The patient may then have an IV inserted so that contrast dye may be injected at some point during testing. The patient is asked to lie on a sliding table-like surface that can be positioned inside the doughnut-shaped ring portion of the MRI machine. The patient will be asked to hold a squeeze-ball to alert the technician in case of an emergency or if the patient suddenly experiences panic due to claustrophobia.
So What About Dental Fillings?
Why, when the technician questions the patient about metal implants and prostheses, are dental fillings generally ignored? Undergoing an MRI test himself, the author asked this question of the attending technician, who gave a clear and logical response. Many metals, such as titanium and non-magnetic surgical steel are used in hip-replacement and other operations. They are well cemented or otherwise attached to the body.
A Dynamic Demonstration
The technician highlighted this by asking me for my locker key and then lightly tossing it toward the inside of the machine. The key rocketed through the air and stuck on the surface of the machine. If allowed to wear metal rings and other ornaments or loose metal implants, the patient might be hurt externally by flying objects or they could conceivably suffer internal injury through uncontrolled movement of the implant. Metal dental fillings are cemented in place and so generally do not move. Besides, they are made of non-magnetic metals, or even non-metallic substances. They pose no problem.
Personal Experience and Conversation with Radiology Technician