title: Characterization of primary and permanent teeth using terahertz spectroscopy.
abstract: OBJECTIVE
  To analyse teeth samples by using terahertz time-domain spectroscopy (THz-TDS) system that was developed in the laboratory to measure the properties of sliced teeth sections in transmission mode.
  
  
  METHODS
  Using home-built THz-TDS system, we analysed a total of 25 teeth samples (9 primary and 16 permanent teeth). For transmission measurements, the refractive index and absorptive properties of the teeth sections were calculated. Difference between groups was tested using Mann-Whitney U-test statistics at the specific frequency of 0.5 THz, which was at the midpoint of the bandwidth. Median and minimum-maximum values were given as descriptive statistics. Type-I error rate was taken as α = 0.05.
  
  
  RESULTS
  Median refractive index values for permanent and primary teeth were found to be 2.53 and 2.54, respectively. Median absorption coefficient values for permanent and primary teeth were found to be 26.29 and 29.67, respectively. Median refractive index values for both healthy and carious teeth were found to be 2.54. Median absorption coefficient values for healthy and carious teeth were found to be 26.52 and 27.13, respectively. Although higher median absorption coefficient values were found for primary and carious teeth than those of permanent and healthy teeth, the differences were insignificant (p > 0.05). In addition, no statistical differences were found for refractive index values among different groups (p > 0.05).
  
  
  CONCLUSIONS
  THz imaging has the potential to be used in assessing dental structures.
authors.affiliation: 1 Department of Dentomaxillofacial Radiology, Faculty of Dentistry, Ankara University, Ankara, Turkey.
authors.forename: K
authors.initials: K
authors.lastname: Kamburoğlu
authors.forename: N Ö
authors.initials: NÖ
authors.lastname: Yetimoĝlu
authors.forename: H
authors.initials: H
authors.lastname: Altan
mesh_terms: D000042:Absorption; D000465:Algorithms; D003731:Dental Caries / Q000378:metabolism / Q000473:pathology; D006801:Humans; D012031:Refractometry; D055068:Terahertz Spectroscopy / Q000379:methods*; D014070:Tooth / Q000033:anatomy & histology / Q000737:chemistry*; D014094:Tooth, Deciduous / Q000033:anatomy & histology / Q000737:chemistry*
keywords: characterization; teeth; terahertz time-domain spectroscopy