Induced magnetic moment in stainless steel components of orthodontic appliances in 1.5 T MRI scanners

Abstract

Purpose: Most orthodontic appliances are made of stainless steel materials and induce severe magnetic susceptibility artifacts in brain MRI. In an effort for correcting these artifacts, it is important to know the value of induced magnetic moments in all parts of orthodontic appliances. In this study, the induced magnetic moment of stainless steel orthodontic brackets, molar bands, and arch-wires from several vendors is measured. Methods: Individual stainless steel brackets, molar bands, and short segments of arch-wire were positioned in the center of spherical flask filled with water through a thin plastic rod. The induced magnetic moment at 1.5 T was determined by fitting the B 0 map to the z-component of the magnetic dipole field using a computer routine.

Correcting B0 Field Distortions in MRI Caused by Stainless Steel Orthodontic Appliances at 1.5 T Using Permanent Magnets – A Head Phantom Study

“…The magnetic moment of individual stand-alone bracket or bracket on dental band was measured one at a time (ref. 13 ) with a precision better than 10 −4 A·m 2 . ( A ) Total magnetic moment of 20 non molar brackets (upper, lower, right and left central incisor, lateral incisor, canine, 1st premolar, 2 nd premolar) (ref.…”

“…( A ) Total magnetic moment of 20 non molar brackets (upper, lower, right and left central incisor, lateral incisor, canine, 1st premolar, 2 nd premolar) (ref. 13 ). ( B ) Total magnetic moment of 8 molar (upper, lower, right, left 1st and 2 nd molar) brackets or brackets on bands.…”

“…Arch wires also possess induced magnetic moment although dominant contributions come from orthodontic brackets and bands. The orthodontic brackets and bands from different vendors differ in weight, shape, material composition, and induced magnetic moment inside the MRI scanner 13 . Fig.…”

“…The magnets were coated with a thin layer of nickel and were custom made to specified sizes (Table 3 ). For each size, the magnetic moment of several samples was measured inside 1.5 T MRI scanner using method described previously 13 . The magnetic moment was anti-parallel to the B 0 field during the measurement.…”

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

“…The need to use MRI on patients wearing orthodontic appliances is not uncommon. During conventional orthodontic treatment, stainless steel brackets are usually bonded to the teeth, and metallic wires are engaged [6]. In these cases, the removal of orthodontic appliance is recommended to avoid image artifacts, unwanted bracket detachment, and an increase in the temperature of the brackets and wires [7,8].…”