title: Magnetic resonance imaging artefacts and fixed orthodontic attachments.
abstract: OBJECTIVE
  Orthodontic appliances are often removed before magnetic resonance imaging (MRI) scans because they are known to produce artefacts. The purpose of this study was to find the exact indications for removal of various fixed attachments when imaging four specific areas of the head and neck.
  
  
  METHODS
  Sixty patients requiring an MRI scan of the head for medical reasons volunteered for this investigation. One of four different types of fixed attachments (stainless steel brackets, titanium brackets, ceramic brackets with metal slots, and stainless steel retainers) were assigned to a patient. Each patient had two scans at 1.5 T: with an 'empty wax jig' and with a wax jig including the attachment. Archwires were not investigated as they are easily removed before a scan. Two radiologists evaluated the scans of each patient and each of the four areas under investigation: maxillary sinus, oral cavity, temporomandibular joints, and posterior cerebral fossa.
  
  
  RESULTS
  Stainless steel brackets always caused non-interpretability of all anatomic areas (100 per cent). Titanium brackets, ceramic brackets with metal slots, and stainless steel retainers caused artefact in the oral cavity only (for 20, 16.65, and 86.65 per cent of the subjects).
  
  
  CONCLUSIONS
  Our results show that ceramic brackets with metal slots and titanium brackets do not always have to be removed before MRI scans of the head and neck, depending on the area under investigation. Metal fixed retainers should only be removed if the oral cavity itself is under investigation. Stainless steel brackets should always be removed before MRI scans of the head and neck.
authors.affiliation: *Faculty of Odontology, Lyon, aurelien.beau@hotmail.fr.
authors.forename: Aurélien
authors.initials: A
authors.lastname: Beau
authors.affiliation: **Center for Medical Imaging Mermoz, Lyon, and.
authors.forename: Denis
authors.initials: D
authors.lastname: Bossard
authors.affiliation: ***Department of Orthodontics, Faculty of Odontology, Lyon, France.
authors.forename: Sarah
authors.initials: S
authors.lastname: Gebeile-Chauty
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016477:Artifacts; D002516:Ceramics; D003722:Dental Alloys; D003799:Dental Stress Analysis / Q000295:instrumentation; D020878:Device Removal; D005260:Female; D006257:Head / Q000473:pathology; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008422:Materials Testing; D008875:Middle Aged; D009532:Nickel; D009967:Orthodontic Appliances; D016910:Orthodontic Brackets; D009969:Orthodontic Wires; D013193:Stainless Steel; D014025:Titanium; D055815:Young Adult
chemical_list: D003722:Dental Alloys; D013193:Stainless Steel; D009532:Nickel; D014025:Titanium