Table 3. Classification of materials based on magnetic susceptibility.

Classification	Description	Significance	Example
Compatible	Compatible: Δx < 3 ppm;	Fully compatible materials;	Resin-based sealer AH Plus, glass ionomer cement, gutta-percha, zirconium dioxide, and some composites.
	Material produces no detectable distortions on either SE or GRE imaging.	Can be present even in the tooth of interest.
Compatible I	Compatible I: 3 < Δx < 200 ppm;	Limited distortions;	Some composites, amalgam, gold alloy, gold-ceramic crowns, titanium alloy, NiTi orthodontic wires
	Material produces noticeable distortions, acceptability depends on application.	Image usability depends on area of interest.
Non-compatible	Non-compatible: Δx > 200 ppm;	Strongest distortions;	Stainless steel orthodontic appliances (wires, brackets), Co-Cr sample.
	Material produces strong image distortions even located far from the imaging region.	Classified as non-compatible.

χ, magnetic susceptibility (synonym = magnetizability); SE, spin-echo; GRE, gradient-echo; compatible I, 3 < Δx < 200 ppm; material produces noticeable distortions, acceptability depends on application.