Magnetic resonance imaging is an increasingly common diagnostic test that doctors use to help detect a range of illnesses and conditions. The test allows your doctor to spot signs of damage or disease, but experts recommend that people with metal devices in their body avoid these scans. Learn more about the risk of MRI scans for people with dental implants, and find out what you need to do if your doctor says you need to have one of these tests.
How an MRI works
Magnetic resonance imaging is a popular choice for doctors because the test is simple and non-invasive. The scan creates detailed cross-sectional images that can aid diagnosis in a way that a basic physical examination could never match.
The test uses a magnetic field and radio-frequency waves to create a series of multi-dimensional images that a doctor can then view on a computer screen. The test is painless and safe for most people, but the powerful magnetic field can interfere with any metal objects inside your body.
Common devices that an MRI scan can interfere with include:
- Cochlear implants
- Implanted drug infusion pumps
- Certain types of contraceptives
- Some metallic dental implants
Patients with these (and other) metallic objects are at risk because the magnetic field can move the metal object. In many cases, even minor movement could cause serious injury. MRI-related injuries are increasingly common in the United States.
Materials that dentists use
It's important to note that MRI scans can only interfere with dental implants that have a high metal content. Dentists use a variety of materials, many of which are safe to have during these diagnostic scans. Researchers classify the magnetic materials that dentists use according to their susceptibility to magnetic fields.
These categories are:
- Ferromagnetic. These materials are strongly magnetic and include cobalt, iron and nickel.
- Paramagnetic. These materials magnetize slightly when placed in the MRI's magnetic field. This group includes magnesium, tin and platinum.
- Diamagnetic. Magnets repel these materials, which include zinc, copper and gold.
Ferromagnetic materials present the highest risk during an MRI scan. The other two categories pose a smaller risk.
Dental injuries that an MRI scan can cause
A magnetic field from an MR system can attract ferromagnetic objects, causing them to move rapidly. This 'missile' effect can cause serious injury to the patient or anyone else in the path of the moving object. In 2001, a boy died in New York when an MRI scanner pulled a metal oxygen tank across the room, leading to serious skull injuries. Although not a dental injury, this incident demonstrates the power of the MR system.
Thermal heating can also occur, where the MR system causes tissue injury at either end of the implant, particularly at the tip, where you will normally see more curvature. The MR system can also dislodge dental implants, causing failure in various dental appliances. The highest risk devices include complete dentures with a metal base, orthodontic wires and brackets, crowns and fixed partial dentures.
Precautions patients should take
When your doctor refers you for an MRI scan, he or she will normally ask if you have any dental implants or devices. Make sure you describe any dental treatment in detail, and ask your dentist for more detailed information if you are unsure about the procedure he or she carried out. As a guiding principle, patients should treat ALL dental implants as unsafe if the dentist is unable to confirm the metallic content. If you have a removable implant, you can still have an MRI scan if you take the device out before the diagnostic.
If your dentist recommends a dental implant, you should discuss the type of implant he or she intends to use. Non-metallic implants (like ceramics) don't pose a risk during an MRI scan. Some metal ceramics that contain a noble metal alloy only pose a minimal risk.
Dental implants improve life for thousands of Americans every year, but metallic implants create risks during MRI diagnostics. Talk to your dentist about the options available to you, and choose the device that best fits your needs. You can learn more by visiting a website like http://www.perioperio.com/.