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Infrared imaging confirms the role of the transparent surface zone in arresting dental caries

  • Liu, Hao1, 2
  • Chang, Nai-Yuan2
  • Gao, Wanrong3
  • Fried, Daniel2
  • 1 Purple Mountain Laboratories, Nanjing, P. R. China, 211111
  • 2 University of California, San Francisco, San Francisco, California, United States, 94143
  • 3 Nanjing University of Science and Technology, Nanjing, P. R. China, 210094
Published Article
Proceedings of SPIE--the International Society for Optical Engineering
Publication Date
Mar 05, 2021
DOI: 10.1117/12.2584907
PMID: 33767521
PMCID: PMC7989780
PubMed Central
  • Article


Several studies have demonstrated the potential of short wavelength infrared (SWIR) reflectance, thermal imaging and optical coherence tomography for the nondestructive assessment of the activity of caries lesions. The purpose of this study was to test the hypothesis that the activity of arrested caries lesions on the coronal surfaces of extracted teeth would be changed by reducing the thickness of the highly mineralized transparent surface layer, which was measured using polarization sensitive optical coherence tomography (PS-OCT). The lesion activity was assessed using SWIR reflectance and thermal imaging during forced air drying of the lesion before and after mechanical removal of a surface layer ~ 50-μm thick covering the lesion. Both the intensity change in SWIR reflectance images at 1500–1750-nm wavelengths after drying the lesions and the change in thermal emission measured with a thermal camera at 8–13-μm wavelengths increased significantly (P<0.05) after reducing the thickness of the mineralized surface layer in the lesions indicating the permeability of the lesion to fluids increased. These results provide further evidence that the presence of a highly mineralized outer surface layer is a key indicator of lesion arrest.

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