Imaging Interproximal and Occlusal Dental Caries with 1310-nm Near-IR Light

Introduction: Dental enamel manifests the highest transparency in the near-IR at 1310-nm, therefore this wavelength is ideally suited for imaging through teeth. Moreover, the attenuation of near-IR light at 1310-nm increases by 2-3 orders of magnitude upon natural and artificial demineralization providing high contrast for imaging dental caries lesions. Objective: To acquire high contrast near-IR images of early interproximal and occlusal caries lesions. Methods: Images of natural and simulated caries in tooth sections and in extracted whole teeth were acquired. Direct transillumination was used to image interproximal lesions employing 1310-nm superluminescent diodes and a InGaAs focal plane array (FPA). Occlusal views were acquired by illumination of the facial surface of the tooth using an elliptical beam of light incident just above the DEJ while viewing the occlusal surface from above with the InGaAs FPA. Results: The attenuation coefficient of enamel increased exponentially from 3 cm-1 to 150 cm-1 with increasing mineral loss in natural caries lesions (r2=0.74, n=100) providing high contrast between sound and demineralized enamel. High contrast images of interproximal lesions were resolved in transillumination. Early occlusal caries, hidden occlusal lesions and even interproximal lesions were visible in near-IR images taken from occlusal views. Moreover, stains and plaque that confound caries detection at visible wavelengths do not absorb near-IR light near 1310-nm allowing easier discrimination of early demineralization. Conclusion: These early images suggest that the near-IR offers significant advantages over the conventional visual, tactile and radiographic caries detection methods. Supported by NIH/NIDCR R01DE14698 research grant.