High contrast near‐infrared polarized reflectance images of demineralization on tooth buccal and occlusal surfaces at λ = 1310‐nm

Abstract

Background and Objectives: 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. Materials and Methods: Fifteen human molars were used in this in vitro study. Teeth were painted with a clear acid-resistant varnish, leaving two 2×2 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). Conclusion: 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.

Evaluation of two imaging techniques: near-infrared transillumination and dental radiographs for the detection of early approximal enamel caries

“…16,18,24 In this study, we demonstrated that the sensitivity and specificity of the NIR TI technique, when compared with radiography, provided very good results. The technique can be useful for early caries diagnosis and patient follow-up, and can improve routine monitoring of enamel lesions during preventive intervention.…”

Near-infrared image-guided laser ablation of dental decay

“…In a recent imaging study, we compared the image contrast of artificially demineralized lesions produced on the buccal and occlusal surfaces on whole extracted teeth measured using various imaging methods. 18 NIR reflectance and NIR transillumination were investigated along with QLF ͑473-nm excitation͒ and visible reflectance. Crossed polarizers were used to eliminate specular reflection ͑glare͒ from tooth surfaces for the NIR and visible light reflectance measurements.…”

Diagnostic Imaging and Spectroscopy

“…Wu and Fried [50] reported the high-contrast polarized reflectance images of early demineralization on buccal and occlusal tooth surfaces measured at l ¼ 1310 nm and found that the contrast between early demineralization was significantly higher at 1310 nm than in the visible range. Figure 68.4a and b show cross-polarization images of enamel demineralization in the visible and NIR region, showing the marked difference in contrast between the sound and demineralized enamel in these two spectral regions.…”