Effect of orthodontic appliances on magnetic resonance images

Abstract

We examined the metallic artifacts created in magnetic resonance images (MRI) of various orthodontic appliances placed on plastic study models. We used steel, ceramic and resin brackets, steel, NiTi, heat-activated NiTi and Beta-Ti orthodontic wires, and steel and elastic ligatures. By six sequences (spine echo for T1 weighted images, fast spine echo for T2 weighted images, fast spine echo for T2 weighted fat suppression images, gradient echo for T2 weighted images, fast gradient echo for 2 dimensional T2 weighted images and fast gradient echo for three dimensional T2 weighted images). A 1.5 tesla super-conductive MRI machine was used to make six sequences of images. A model that adapted steel brackets, steel wire and steel ligatures produced the largest metallic artifacts in the MRI. A model with steel brackets alone produced large metallic artifacts while a model with ceramic brackets and Ti wire did not produce large metallic artifacts. In addition to the signal loss caused by the metallic artifacts, image distortion was spread over a wide area. We concluded that orthodontists should not use steel orthodontic brackets and wires for patients who expect to have MRI of the head and neck region.