Evaluation of magnetic resonance imaging artifacts caused by fixed orthodontic CAD/CAM retainers—an in vitro study
Christoph J. Roser, Tim Hilgenfeld, Sinan Şen, Tobias Badrow, Sebastian Zingler, Sabine Heiland, Martin Bendszus, Christopher J. Lux, Alexander Juerchott
Abstract
Abstract Objectives Magnetic resonance imaging (MRI) image quality can be severely impaired by artifacts caused by fixed orthodontic retainers. In clinical practice, there is a trend towards using computer-aided design/computer-aided manufacturing (CAD/CAM) retainers. This study aimed to quantify MRI artifacts produced by these novel CAD/CAM retainers. Material and methods Three CAD/CAM retainers and a stainless-steel retainer (“Twistflex”; clinical reference standard) were scanned in vitro at 3-T MRI using a high-resolution 3D sequence. The artifact diameters and three-dimensional artifact volumes (AV) were determined for all mandibular (AV mand ) and maxillary (AV max ) retainers. Moreover, the corresponding ratio of artifact volume to retainer volume (AV/RV mand , AV/RV max ) was calculated. Results Twistflex caused large artifact volumes (AV mand : 13530 mm 3 ; AV max : 15642 mm 3 ; AV/RV mand : 2602; AV/RV max : 2235). By contrast, artifact volumes for CAD/CAM retainers were substantially smaller: whereas artifact volumes for cobalt–chromium retainers were moderate (381 mm 3 ; 394 mm 3 ; 39; 31), grade-5 titanium (110 mm 3 ; 126 mm 3 ; 12; 12) and nickel–titanium (54 mm 3 ; 78 mm 3 ; 12; 14) both produced very small artifact volumes. Conclusion All CAD/CAM retainers caused substantially smaller volumes of MRI artifacts compared to Twistflex. Grade-5 titanium and nickel–titanium CAD/CAM retainers showed the smallest artifact volumes. Clinical relevance CAD/CAM retainers made from titanium or nickel–titanium may not relevantly impair image quality in head/neck and dental MRI. Artifacts caused by cobalt–chromium CAD/CAM retainers may mask nearby dental/periodontal structures. In contrast, the large artifacts caused by Twistflex are likely to severely impair diagnosis of oral and adjacent pathologies.