Fixed Orthodontic Appliances under Magnetic Resonance Imaging: An Integrated Analysis of Temperature Increase and Bonding Efficacy

Introduction: Magnetic resonance imaging (MRI) is increasingly required in orthodontic patients wearing fixed metallic appliances. Concerns regarding device heating, debonding, and potential safety risks often lead clinicians to remove orthodontic appliances before MRI examinations, despite limited evidence supporting this practice. This study provides an integrated analysis of three previously published in vitro investigations evaluating the effects of 1.5 T and 3 T MRI on the thermal behaviour and bonding efficacy of fixed orthodontic devices.

Methods: Different fixed orthodontic appliances, including stainless-steel brackets and archwires, molar bands with welded tubes, and multibraided fixed retainers of varying diameters, were evaluated following exposure to 1.5 T and 3 T MRI. Outcomes included temperature variation before and after MRI exposure, shear bond strength (SBS), and adhesive remnant index (ARI). All data were statistically analysed, with significance set at p < 0.05.

Results: All studies reported statistically significant temperature increases in some experimental groups following MRI exposure, particularly at 3 T. However, heating remained clinically negligible, generally below 2.5 °C and frequently below 1 °C. No clinically relevant differences were found among appliance types, wire dimensions, or bonding materials. MRI exposure did not significantly affect SBS values, indicating preservation of appliance adhesion. Although minor changes in ARI distribution were reported for brackets and wires, no increased debonding risk was observed. Overall, orthodontic devices maintained adequate mechanical performance after MRI examination.

Conclusions: Current evidence suggests that fixed metallic orthodontic appliances, including brackets, bands, and multibraided retainers, are safe during 1.5 T and 3 T MRI examinations. Minimal temperature increases and unchanged bond strength values indicate that routine appliance removal is generally unnecessary and should be considered only when image artifacts may compromise diagnostic quality in the region of interest.