A Magnetic Resonance Imaging (MRI) scan uses strong magnetic fields and radio waves to generate highly detailed pictures of organs and soft tissues inside the body. The presence of metal within the body, such as the components found in dental braces, presents a common consideration when a patient is scheduled for this type of imaging. Understanding the interaction between the MRI machine and orthodontic appliances is necessary to determine if a scan is possible and what steps must be taken to ensure both patient safety and image quality. This article clarifies the circumstances under which an MRI scan can be performed with braces and outlines the necessary preparation.
Feasibility and Safety Considerations
The possibility of undergoing an MRI with braces depends primarily on the material composition of the orthodontic appliance and the specific area of the body being scanned. Traditional braces often contain stainless steel, which is a ferromagnetic metal, meaning it is attracted to a magnetic field. This interaction introduces two main physical safety concerns for the patient.
The first safety concern involves the movement or displacement of the metal components within the intense magnetic field of the scanner. While braces are generally fixed securely to the teeth, the deflection force exerted on ferromagnetic metals can cause the appliance to shift or vibrate. The second, more significant safety risk is the potential for radiofrequency (RF) heating, which occurs when the wires act as small antennas that absorb the energy transmitted by the MRI scanner.
This absorbed energy can induce electrical currents within the metal, causing the surrounding tissue to heat up. Studies examining this thermal effect have found that temperature changes are usually within acceptable clinical ranges, but the risk varies significantly based on the specific alloy used and the length of the archwire. Consequently, while modern orthodontic materials like titanium alloys or ceramic brackets are considered much safer and sometimes even “MR safe,” traditional stainless steel components require careful verification before the patient enters the scanner.
How Braces Affect MRI Results
Even when safety concerns are minimal, the metal in braces introduces an issue that can severely limit the diagnostic value of the scan: the creation of imaging artifacts. This phenomenon is known as magnetic susceptibility artifact, and it occurs because the metal disrupts the uniformity of the local magnetic field generated by the MRI scanner.
The metal components cause the magnetic field lines to distort around the appliance, resulting in signal loss or distortion in the final image. This effect is visualized as a large, dark void—a signal void—surrounding the metal, often accompanied by geometric distortion or bright signal areas at the edges of the void. The size and severity of this artifact depend directly on the type of metal, with stainless steel generating the largest artifacts, followed by cobalt-chromium, while titanium alloys produce much smaller disturbances.
The diagnostic impact is directly related to the proximity of the braces to the area being imaged. For scans of the head, neck, orbits, or brain, the artifacts from braces can obscure anatomical details in the facial region, frontal lobe, or pituitary gland, rendering the images diagnostically unusable for those areas. However, if the area of interest is distant from the mouth, such as a knee or spine scan, the effect of the braces is negligible. Specialized imaging techniques, such as those that use fast spin echo sequences or dedicated metal artifact reduction sequences, can sometimes minimize the size of these distortions, potentially allowing for a usable image.
Preparing for the Scan
The first action a patient should take upon scheduling an MRI is to consult with both the referring physician and the orthodontist to discuss the presence of braces. The orthodontist is the only person who can accurately identify the exact material composition of the brackets and wires, which is necessary for the radiology team to assess the risk. Stainless steel requires further evaluation.
If the scan is necessary for the head or neck region, the orthodontist may recommend mitigation strategies. This could involve the temporary removal of the archwires, which are the most magnetically reactive components, or the replacement of stainless steel wires with non-ferromagnetic alternatives, such as nickel-titanium or titanium molybdenum alloys. In some cases, the entire appliance may need to be temporarily removed, particularly if the diagnostic information is time-sensitive and cannot be obtained otherwise. Before the patient enters the MRI suite, they must provide full disclosure of all remaining metallic components to the MRI technologist, who will then ensure the correct imaging protocols are used to maximize safety and image quality.