title: Dental bur fragments causing metal artifacts on MR images.
abstract: OBJECTIVE
  Our purpose was to define the role of dental bur fragments in producing metal artifacts on MR images.
  
  
  METHODS
  Dental prosthetic reconstructions were made for two dogs. The two lower second premolars were prepared for full-cast crowns by using a diamond bur. The crown margin was placed subgingivally on the right side (1 mm below the free gingival margin) and at the same level as the free gingival margin on the left side. After 1 week, full-cast crowns were cemented in place. MR imaging was performed 7 days later.
  
  
  RESULTS
  Metal artifacts appeared in both second premolar regions of the mandible on MR images, with the right side, in which the crown margin was positioned subgingivally, displaying a larger signal distortion than the left side. After removal of the crown, the artifact remained on the right. On histopathologic examination, bur fragments were detected in the gingiva, more on the right than on the left. X-ray fluorescent element analysis showed iron in the gingival tissue containing bur fragments.
  
  
  CONCLUSIONS
  Distortion of MR images was considered to be attributable in part to the damage of the gingiva and in part to the presence of dental bur fragments.
authors.affiliation: Department of Radiology, Massachusetts Eye and Ear Infirmary and Harvard Medical School, Boston 02114, USA.
authors.forename: T
authors.initials: T
authors.lastname: Kaneda
authors.forename: M
authors.initials: M
authors.lastname: Minami
authors.forename: H D
authors.initials: HD
authors.lastname: Curtin
authors.forename: T
authors.initials: T
authors.lastname: Utsunomiya
authors.forename: I
authors.initials: I
authors.lastname: Shirouzu
authors.forename: M
authors.initials: M
authors.lastname: Yamashiro
authors.forename: H
authors.initials: H
authors.lastname: Kiba
authors.forename: H
authors.initials: H
authors.lastname: Yamamoto
authors.forename: S
authors.initials: S
authors.lastname: Ohba
mesh_terms: D000818:Animals; D016477:Artifacts; D001641:Bicuspid / Q000473:pathology; D003442:Crowns; D003775:Dental Polishing / Q000295:instrumentation*; D004285:Dogs; D005547:Foreign Bodies / Q000473:pathology*; D005881:Gingiva / Q000473:pathology*; D007501:Iron / Q000378:metabolism*; D008279:Magnetic Resonance Imaging; D008334:Mandible / Q000473:pathology
chemical_list: D007501:Iron