Quantification of Artifacts in MR Images Caused by Commonly Used Dental Materials

Background: Although new approaches for application of magnetic resonance imaging (MRI) in dentistry have been promising, the presence of dental materials in the oral cavity represents a major obstacle to generating quality MRI data. The resulting artifacts can adversely affect diagnostic accuracy of oral and maxillofacial conditions. Objectives: This study aimed to detect and assess artifacts caused by metallic and non-metallic dental materials in MR images. Materials and Methods: Nineteen commonly used dental materials were used in an in vitro assay. An empty cube-shaped phantom with internal dimensions of 15 x 15 x 15 cm(3) was fabricated of polyester and filled with paraffin or distilled water to create optimal contrast for T1-weighted (T1W; for anatomical structures), T2-weighted (T2W, for pathological conditions) and proton density-weighted (PDW) MR images. Dental material samples were manufactured and placed at the center of the mold using polyester tubes. All samples were then subjected to MRI using two-dimensional (2D) and three-dimensional (3D) T1W, T2W and PDW imaging sequences. The data were subjected to one-way analysis of variance (ANOVA) followed by mean comparison using the Tukey's test. Results: Comparison of mean artifact size in 2D and 3D images showed that ceramic caused the smallest (189.48 mm(3)) and orthodontic metal brackets caused the largest (4307.5 mm(3)) artifact areas. Assessment of the amount of artifacts created in different imaging sequences revealed minimal artifact in inversion recovery sequence and maximum artifact in gradient echo sequence of the amount of artifacts at different weighing times in 2D and 3D images showed minimal artifacts in PDW and maximum artifacts in T2W. Conclusion: Bracket, titanium implants, and the nickel-chromium (Ni-Cr) materials are the three most susceptible materials to external B0 magnetic field; thus creating huge metal-induced artifacts. The Siemens default two dimensional turbo spin echo (2D-TSE), 2D-BLADE, three dimensional volumetric interpolated breath-hold examination (3D-VIBE) and three dimensional sampling perfection with application optimized contrasts using different flip angle evolution (3D-SPACE) are the most appropriate pulse sequences for the 2D-T1W, 2D-T2W, 3D-T1W, and 3D-T2W evaluations of the bracket/titanium/Ni-Cr materials, respectively. The rest of the materials' magnetic susceptibility effects are negligible, and artifacts are small.