Influence of orthodontic appliance-derived artifacts on 3-T MRI movies

Abstract

BackgroundMagnetic resonance imaging (MRI) has been used to study configurations of speech organs in the resting state. However, MRI is sensitive to metals, and numerous types of metallic appliances, most of which have a large magnetic susceptibility, are used in orthodontic treatment and may cause severe artifacts on MRI. We have developed techniques for obtaining MRI movies of the oral region, to evaluate articulatory changes, especially movement of the tongue, palate, and teeth, pre- and post-orthodontic/orthognathic treatment. We evaluated the influence of artifacts caused by orthodontic appliances, including fixed retainers, metal brackets, and wires, on measurements in 3-T MRI movies.MethodsSixteen healthy young adults (nine males, seven females; average age, 27 years) with normal occlusion were recruited. Four types of customized maxillary and mandibular plates were prepared by incorporating one of the following into the plate: (a) nothing, (b) a fixed canine-to-canine retainer, (c) metal brackets for the anterior and molar teeth, or (d) clear brackets for the anterior teeth and metal brackets for molars. A 3-T MRI movie, in segmented cine mode, was generated for each plate condition while participants pronounced a vowel-consonant-vowel syllable (/asa/). The size of the artifact due to the metallic brackets was measured. The face size and orthodontically important anatomical structures, such as the velum, the hard palate, and the laryngeal ventricle, were also measured.ResultsA large artifact was observed over the entire oral region around orthodontic appliances, altering regional visibility. The velopharyngeal height was measured as significantly longer in the presence of metal brackets. The maximum artifact size due to a metallic bracket was > 8 cm. Our results show that even if it is possible to obtain the measurements of palate length, nasion to sella, and nasion to basion in individuals wearing metal brackets for molars, the measurements might be affected due to the presence of artifacts.ConclusionsOrthodontic appliances, including metallic materials, sometimes produce significant measurement error in speech evaluation using MRI movies, which often become invisible or distorted by metallic orthodontic appliances. When the distorted image is measured, caution should be exercised, as the measurement may be affected. Based on the study, it is concluded that orthodontists should not necessarily remove all metallic appliances before MRI examination because the influence varies among the appliances and should also know that a significant measurement error in speech evaluation using MRI movie may occur by image distortion caused by metallic artifacts.

Magnetic Resonance Imaging and Its Effects on Metallic Brackets and Wires: Does It Alter the Temperature and Bonding Efficacy of Orthodontic Devices?

“…A classification of dental materials according to their magnetic susceptibility has been proposed [33], and studies have evaluated the effects of orthodontic fixed metal appliances [34] and retainers [35] on image quality. There is fair evidence to suggest that orthodontic devices cause MRI image artefacts both at 1.5 T [8] and 3 T [36]. The removal of metal orthodontic devices prior to MRI is thus recommended, especially if the area of interest is near the appliance [5,37], as in cervical vertebrae, cervical region, paranasal sinuses, and head and neck MRI scans.…”

“…The removal of metal orthodontic devices prior to MRI is thus recommended, especially if the area of interest is near the appliance [5,37], as in cervical vertebrae, cervical region, paranasal sinuses, and head and neck MRI scans. A brain and temporomandibular joint region MRI should not, however, require the removal of such appliances [36].…”

New application of dynamic magnetic resonance imaging for the assessment of deglutitive tongue movement

“…Because this posture might have affected the exact time course of deglutition, further studies to capture images in a sitting position should be conducted [ 22 ]. Finally, the dynamic images often become invisible or distorted and linear measurements may be incorrect because metallic appliances in the oral cavity, such as orthodontic appliances, produce a range of artifacts depending on the location and type of metal [ 23 ]. The authors concluded, however, that orthodontists should not necessarily remove all metallic appliances before MRI examination and that caution should be exercised when the distorted image is measured.…”

Preliminary study of articulatory characteristics in open bite subjects revealed by 3T magnetic resonance imaging movies

“…MR movies are suitable for the evaluation of tongue movement. According to a study of patients with orthodontic appliances, [29] it is difficult to analyze the state during orthodontic treatment using MR movies. However, to perform an MR movie before, during, and after MFT will be meaningful to improve patient motivation.…”