Influence of common fixed retainers on the diagnostic quality of cranial magnetic resonance images

Miriam Shalish*, Nimrod Dykstein, Silvina Friedlander-Barenboim, Eliel Ben-David, John Moshe Gomori, Stella Chaushu

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    15 Scopus citations


    Introduction Orthodontists are often asked to remove fixed retainers before magnetic resonance imaging (MRI). This study was undertaken to assess the effects of 2 commonly used fixed retainers on MRI distortion and whether they should be removed. Methods MRI scans were performed on a dry skull with Twistflex (Dentaurum, Ispringen, Germany) and Ortho Flex Tech (Reliance Orthodontic Products, Itasca, Ill) retainers. Two neuroradiologists independently ranked the distortions. The influence of the fixed retainers' alloys, their distance to the area of diagnosis, location, strength of the magnetic field, and the spin-echo sequence were examined. Statistical analysis included kappa and Pearson chi-square tests. Results Ortho Flex Tech retainers caused no distortion. Twistflex retainers caused distortion in 46% of the tests in areas close to the retainer (tongue and jaws). Maxillary fixed retainers and the combination of maxillary and mandibular fixed retainers further increased the distortion. Greater distortion was observed with 3-T magnetic fields and T1-weighted spin-echo sequences. Conclusions Removal of the Ortho Flex Tech retainer is unnecessary before MRI. Removal of the Twistflex should be considered if the MRI scans are performed to diagnose areas close to the fixed retainers, when 3-T magnetic fields and T1-weighted sequences are used, and when both maxillary and mandibular fixed retainers are present.

    Original languageAmerican English
    Pages (from-to)604-609
    Number of pages6
    JournalAmerican Journal of Orthodontics and Dentofacial Orthopedics
    Issue number5
    StatePublished - 1 May 2015

    Bibliographical note

    Publisher Copyright:
    © 2015 American Association of Orthodontists.


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