Evidence shows that fixed metal dental retainers are indeed affected by MRI magnetic fields, primarily by producing magnetic susceptibility artifacts that can distort imaging and reduce diagnostic quality.
The claim states that fixed metal dental retainers are not affected by MRI magnetic fields. However, multiple literature reviews, in vitro, and in vivo studies (e.g., papers [0], [1], [6], [7], and [8]) clearly demonstrate that metal orthodontic retainers interact with MRI magnetic fields, resulting in mechanical displacement, heating concerns, and significant image artifacts. Therefore, the claim is refuted by the available evidence.