Artifacts in MRI caused by different types of fixed orthodontic appliance - An in vitro study

Aims: The overall aim was to establish the degree of artifacts made by orthodontic appliances in MRI. Specific aim was to investigate if any sequences applied at the investigation could improve the images quality. Materials and Methods: Twelve frequently used orthodontic appliances were tested. The appliances were cemented/bonded on twelve study casts placed in translucent plastic boxes filled with water and contrast. The MRI expositions were performed in a 1.5 Tesla and 3 Tesla scanners respectively (1.5 T: MAGNETOM AvantoFit, 3 T: MAGNETOM Trio, Siemens Healthcare, Erlangen, Germany). The used imaging sequences to reduce the artifacts were 1) turbo spin echo (TSE), 2) TSE combined with view angle tilting (VAT), and 3) TSE with both VAT and slice encoding for metal artifact correction (SEMAC). Results: After the MR imaging and the artifacts reduce imaging sequences technique (TSE, TSE combined with VAT and TSE with VAT and SEMANC) the Orto-pro nickel free brackets showed the largest amount of image artifacts, while the gold chain, titanium brackets and buccal mini-screws showed smallest artifact. TSE with both VAT and SEMAC artifact reduction imaging sequences were the best sequence to improve MRI quality. Conclusion: Titanium brackets showed the smallest artifact compared to conventional and nickel free brackets. TSE with both VAT and SEMAC imaging sequence to reduce the artifacts was superior in improving image quality than the TES and TES combined with VAT