Quantification of artifacts caused by fixed retainers in dental-dedicated MRI-a descriptive in vitro study

Magnetic resonance imaging (MRI) is emerging as a promising tool in dental diagnostics, especially at lower field strengths like 0.55T which reduces metal-induced artifacts compared to conventional 1.5T. This study aimed to quantify the artifacts produced by common fixed lingual retainers using a dental-dedicated MRI (ddMRI) system.

Six orthodontic fixed retainers were scanned in vitro with a 0.55T ddMRI system using a proton density pulse sequence. Artifacts were measured in four cross-sectional planes-axial, sagittal, coronal, and oblique-and superimposed onto a CBCT volume to evaluate distortion of anatomical structures.

Stainless steel (SS) retainers produced the largest artifacts, with 0.0195 SS Coaxial causing the most distortion, followed by 0.030 SS Round, 0.0215 SS Coaxial, and Ortho Flextech SS. These retainers significantly obscured the anterior oral cavity. In contrast, 0.030 Blue Elgiloy and 0.028 titanium molybdenum alloy (TMA) generated smaller artifacts, affecting only the mandibular anterior crowns while sparing other head and neck structures.

Retainer material significantly impacts artifact size in ddMRI. Nonstainless-steel options, especially 0.028 TMA and 0.030 Blue Elgiloy, produce smaller sized artifacts and preserve more anatomical visibility, improving the potential for accurate diagnosis.