title: High contrast near-infrared polarized reflectance images of demineralization on tooth buccal and occlusal surfaces at lambda = 1310-nm.
abstract: OBJECTIVE
  Sound enamel manifests peak transparency in the near-IR (NIR) at 1310-nm, therefore the near-IR is ideally suited for high contrast imaging of dental caries. The purpose of this study was to acquire images of early demineralized enamel on the buccal and occlusal surfaces of extracted human teeth using NIR reflectance imaging and compare the contrast of those images with the contrast of images taken using other methods.
  
  
  METHODS
  Fifteen human molars were used in this in vitro study. Teeth were painted with a clear acid-resistant varnish, leaving two 2 mm x 2 mm windows on the buccal and occlusal surfaces of each tooth for demineralization. Artificial lesions were produced in the exposed windows after a 2-day exposure to a demineralizing solution at pH 4.5. Lesions were imaged using NIR transillumination, NIR and visible light reflectance, and fluorescence imaging methods. Crossed polarizers were used where appropriate to improve contrast. Polarization sensitive optical coherence tomography (PS-OCT) was also used to non-destructively assess the depth and severity of demineralization in each sample window.
  
  
  RESULTS
  NIR reflectance imaging had the highest image contrast for both the buccal and occlusal groups and it was significantly higher contrast than visible light reflectance (P < 0.05).
  
  
  CONCLUSIONS
  The results of the study suggest that NIR reflectance imaging is a promising new method for acquiring high contrast images of early demineralization on tooth surfaces.
authors.affiliation: Department of Growth and Development, University of California, San Francisco, California 94143-0758, USA.
authors.forename: J
authors.initials: J
authors.lastname: Wu
authors.forename: D
authors.initials: D
authors.lastname: Fried
mesh_terms: D000704:Analysis of Variance; D003732:Dental Caries Activity Tests / Q000295:instrumentation / Q000379:methods*; D003743:Dental Enamel / Q000473:pathology; D005453:Fluorescence; D006801:Humans; D007091:Image Processing, Computer-Assisted; D066298:In Vitro Techniques; D007259:Infrared Rays; D008027:Light; D008857:Microscopy, Interference; D013499:Surface Properties; D041623:Tomography, Optical Coherence; D017001:Tooth Demineralization / Q000175:diagnosis*; D014172:Transillumination / Q000295:instrumentation / Q000379:methods*