Dental fillings are restorative materials used to repair teeth damaged by decay or trauma. Whether these fillings are magnetic depends entirely on their material composition. While some fillings contain metals, they are not typically ferromagnetic, meaning they are not strongly attracted to a magnet like iron. Their magnetic characteristics range from minimal qualities to being entirely non-magnetic.
The Materials Science of Fillings
The magnetic behavior of a dental filling is determined by its material science, which separates substances into three main categories of magnetism. Ferromagnetic materials, like iron or nickel, are strongly attracted to magnets and retain their own magnetic properties. Most dental materials are not ferromagnetic; instead, they exhibit either paramagnetic or diamagnetic characteristics. Paramagnetic materials are slightly attracted to a magnetic field, while diamagnetic materials are weakly repelled by it.
The two most common filling types are amalgam and composite resin. Amalgam, often called a silver filling, is a durable alloy made primarily of silver, tin, copper, and liquid mercury. The final, cured amalgam is not ferromagnetic; it is classified as weakly diamagnetic or paramagnetic, which is why it will not stick to a refrigerator magnet. Composite resin is composed of an acrylic matrix reinforced with glass or ceramic particles. Since composite fillings do not contain significant metal, they are considered non-magnetic.
Fillings and Magnetic Resonance Imaging
The primary concern regarding the magnetism of dental restorations involves the powerful magnetic fields used in Magnetic Resonance Imaging (MRI) scans. Although fillings are not strongly magnetized enough to be dislodged, their metallic content can significantly interfere with the scan itself. This interference manifests as signal dropouts or bright streaks on the image, a phenomenon known as an artifact. These artifacts make it difficult to visualize nearby soft tissues, such as the jaw, brain stem, or sinuses, obscuring the diagnostic view.
The metallic components in amalgam are the main cause of these artifacts due to their magnetic susceptibility. This susceptibility is a measure of how much a material becomes magnetized in an external field. While the widely used 1.5-Tesla MRI machines are considered safe, some research indicates that ultra-high-field MRI machines, such as the 7-Tesla models, may cause a measurable increase in mercury release from amalgam fillings. Patients undergoing an MRI should always inform the technologist about the type and location of any dental restorations.
Interaction with Everyday Electronics
The minimal magnetic properties of dental fillings mean they have virtually no practical interaction with the weaker magnetic fields encountered in daily life. Common concerns, such as triggering airport security metal detectors, are unfounded for standard dental restorations. The small metal mass and the non-ferromagnetic nature of the materials are insufficient to set off the sensors.
Electronic devices like cell phones or security tags are similarly unaffected by the presence of dental fillings. The magnetic fields generated by these electronics are too weak to interact meaningfully with the materials in amalgam or composite. Individuals with dental fillings do not need to take special precautions when using personal electronics or passing through security checkpoints.