Influence of dental materials on dental MRI

Abstract

Objectives: To investigate the potential influence of standard dental materials on dental MRI (dMRI) by estimating the magnetic susceptibility with the help of the MRI-based geometric distortion method and to classify the materials from the standpoint of dMRI. Methods: A series of standard dental materials was studied on a 1.5 T MRI system using spin echo and gradient echo pulse sequences and their magnetic susceptibility was estimated using the geometric method. Measurements on samples of dental materials were supported by in vivo examples obtained in dedicated dMRI procedures. Results: The tested materials showed a range of distortion degrees. The following materials were classified as fully compatible materials that can be present even in the tooth of interest: the resinbased sealer AH Plus ® (Dentsply, Maillefer, Germany), glass ionomer cement, gutta-percha, zirconium dioxide and composites from one of the tested manufacturers. Interestingly, composites provided by the other manufacturer caused relatively strong distortions and were therefore classified as compatible I, along with amalgam, gold alloy, gold-ceramic crowns, titanium alloy and NiTi orthodontic wires. Materials, the magnetic susceptibility of which differed from that of water by more than 200 ppm, were classified as non-compatible materials that should not be present in the patient's mouth for any dMRI applications. They included stainless steel orthodontic appliances and CoCr. Conclusions: A classification of the materials that complies with the standard grouping of materials according to their magnetic susceptibility was proposed and adopted for the purposes of dMRI. The proposed classification can serve as a guideline in future dMRI research.

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

“…Significant artifacts created by orthodontic metal brackets have also been reported in previous studies (6,(8)(9)(10)(11)(12)(13). Insignificant artifacts caused by ceramics were also reported by Asano et al (8) and Beau et al (9) who stated that ceramic brackets should not be necessarily removed from the oral cavity prior to MRI.…”

“…The spin echo sequences included turbo spin echo, 3D turbo spin echo, BLADE and 3D space. Gradient echo sequences included 2D FLASH, 6 Iran J Radiol. In Press(In Press):e55566.…”

“…In 2013, Timofiyeva et al (6) evaluated the effect of dental materials on MR images in vitro and in vivo and showed that dental materials could be classified into three groups of compatible, I compatible and incompatible in this respect. Incompatible dental materials should not be present in the oral cavity during MRI.…”

Should the orthodontic brackets always be removed prior to magnetic resonance imaging (MRI)?

“…Table 2 shows detailed suggestions based on current literature. 1,3,16,22,24,26,27,30 It should be mentioned that the degree of image distortion varies inter-individually and highly depends on ferromagnetic content of the alloys and products. 22 In conclusion, not all the brackets should be removed before the MR imaging and particular decision should be made individually considering the area of interest to be studied and type of brackets worn.…”

Induced magnetic moment in stainless steel components of orthodontic appliances in 1.5 T MRI scanners

“…17 There were also studies quantifying MRI artifacts from dental materials. 18 From a diagnostic imaging physics viewpoint, detailed composition of commercial orthodontic brackets, bands, and wires in patients is not known, and the weights of these components are also variable. The induced magnetic moment is the quantity that directly relates to the B 0 inhomogeneity.…”