title: Magnetic resonance imaging of solid dental restoration materials using 3D UTE sequences: visualization and relaxometry of various compounds.
abstract: OBJECTIVE
  Due to an increasing scientific interest in MR-imaging of carious lesions and teeth, an accurate signal characterization of dental restoration materials is necessary for optimization of MR sequence protocols and evaluation of material degradation. Therefore, signal yield and relaxation behavior of common dental restoration materials in comparison to those of dentine of extracted human teeth were assessed in vitro by ultrashort echo time (UTE) sequences.
  
  
  METHODS
  Eighteen material samples and dentine of two freshly extracted human teeth were investigated on a 3T whole-body clinical MR-scanner. Transverse (T2*) and longitudinal relaxation times (T1) were quantified using a recently published modified Ernst equation that takes relevant in-pulse relaxation effects into account.
  
  
  RESULTS
  All investigated samples could be successfully visualized but maximum signal yield was highly variable between samples. T1-values of the investigated dental restoration materials ranged between 28 and 365 ms, whereas T2*-values ranged between 96 and 917 μs. In contrast, T1-values of dentine (T1=545 ms±299 ms) were higher, while T2*-values (T2*=478 μs±271 μs) showed similar values.
  
  
  CONCLUSIONS
  Dental restoration materials and dentine of extracted human teeth can be visualized by UTE sequences and show a broad range of signal yield and relaxation times.
authors.affiliation: Department of Diagnostic and Interventional Radiology, University Hospital Tuebingen, Hoppe-Seyler-Strasse 3, 72076, Tübingen, Germany, ulrich.grosse@med.uni-tuebingen.de.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Grosse
authors.forename: Roland
authors.initials: R
authors.lastname: Syha
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Papanikolaou
authors.forename: Petros
authors.initials: P
authors.lastname: Martirosian
authors.forename: Gerd
authors.initials: G
authors.lastname: Grözinger
authors.forename: Christoph
authors.initials: C
authors.lastname: Schabel
authors.forename: Fritz
authors.initials: F
authors.lastname: Schick
authors.forename: Fabian
authors.initials: F
authors.lastname: Springer
mesh_terms: D016477:Artifacts; D003764:Dental Materials / Q000737:chemistry*; D003804:Dentin / Q000737:chemistry; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008963:Molar / Q000473:pathology* / Q000502:physiology; D015203:Reproducibility of Results; D059629:Signal-To-Noise Ratio; D014070:Tooth / Q000473:pathology* / Q000502:physiology
chemical_list: D003764:Dental Materials