Research on the detection of early caries based on hyperspectral imaging

Objective: We applied hyperspectral imaging (HSI) system to distinguish early caries from sound and pigmented areas. It will provide a theoretical basis and technical support, for research and development of an instrument that could be used for screening and detection of early dental caries. Methods: Eighteen extracted human teeth (molars and premolars), with varying degrees of natural pathology and no degree of decay involving dentin were obtained. HSI system with a wavelength range from 400 to 1000 nm was used to obtain images of all 18 teeth containing sound, carious and pigmented areas. We compared the spectra of the wavebands at both 500 nm and 780 nm from the different tooth states, and the reflectance difference between sound versus carious lesions and sound versus pigmented areas, respectively. Results: There was a slight difference in reflectance between carious areas and pigmented areas at 500 nm. A substantial difference was additionally noted in reflectance between carious areas and pigmented areas at 780 nm. Conclusion: The results have shown that the interference of tooth surface pigment can be eliminated in the near-infrared (NIR) waveband, and the caries can be effectively identified from the pigmented areas. Thus, it could be used to detect carious areas of teeth in place of the traditional visual inspection method or white light endoscopy.