Abstract
ObjectivesMagnetic 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 methodsThree 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 (AVmand) and maxillary (AVmax) retainers. Moreover, the corresponding ratio of artifact volume to retainer volume (AV/RVmand, AV/RVmax) was calculated.ResultsTwistflex caused large artifact volumes (AVmand: 13530 mm3; AVmax: 15642 mm3; AV/RVmand: 2602; AV/RVmax: 2235). By contrast, artifact volumes for CAD/CAM retainers were substantially smaller: whereas artifact volumes for cobalt–chromium retainers were moderate (381 mm3; 394 mm3; 39; 31), grade-5 titanium (110 mm3; 126 mm3; 12; 12) and nickel–titanium (54 mm3; 78 mm3; 12; 14) both produced very small artifact volumes.ConclusionAll 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 relevanceCAD/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.
Highlights
Magnetic resonance imaging (MRI) is an essential, nonionizing imaging technique that is increasingly being used to diagnose disorders of the head and neck region [1]
Among the computer-aided design/computer-aided manufacturing (CAD/CAM) retainers tested, the largest artifact volumes were recorded for the cobalt–chromium CAD/CAM retainers
3D volumes of MRI artifacts caused by three novel CAD/CAM retainers made from cobalt–chromium, grade-5 titanium, and nickel– titanium were determined for the first time and compared with
Summary
Magnetic resonance imaging (MRI) is an essential, nonionizing imaging technique that is increasingly being used to diagnose disorders of the head and neck region [1]. Unlike the traditional manufacturing process of conventional retainers, more and more manufacturers are offering computer-aided design/computer-aided manufacturing (CAD/CAM) techniques based on intraoral scans or digitized plaster models. These CAD/CAM retainers differ with regard to the materials (mostly cobalt–chromium, titanium, and nickel–titanium) and production techniques used. An in vitro study revealed that CAD/CAM NiTi retainers have better biomechanical properties than conventional Twistflex retainers [26]. Because they offer the practitioner further advantages in addition to those already mentioned, it can be assumed that CAD/CAM retainers will become increasingly popular. The material of the retainer and the area of interest should be considered when deciding whether retainers should be removed
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