Multispectral near-infrared reflectance and transillumination imaging of occlusal carious lesions: Variation in lesion contrast with lesion depth

Abstract

In vivo and in vitro studies have demonstrated that near-infrared (NIR) light at λ=1300-1700-nm can be used to acquire high contrast images of enamel demineralization without interference of stains. The objective of this study was to determine if a relationship exists between the NIR image contrast of occlusal lesions and the depth of the lesion. Extracted teeth with varying amounts of natural occlusal decay were measured using a multispectral-multimodal NIR imaging system which captures λ=1300-nm occlusal transillumination, and λ=1500-1700-nm cross-polarized reflectance images. Image analysis software was used to calculate the lesion contrast detected in both images from matched positions of each imaging modality. Samples were serially sectioned across the lesion with a precision saw, and polarized light microscopy was used to measure the respective lesion depth relative to the dentinoenamel junction. Lesion contrast measured from NIR cross-polarized reflectance images positively correlated (p<0.05) with increasing lesion depth and a statistically significant difference between inner enamel and dentin lesions was observed. The lateral width of pit and fissures lesions measured in both NIR cross-polarized reflectance and NIR transillumination positively correlated with lesion depth.

Keywords: detection; multimodal; near-IR imaging; occlusal carries; reflectance; transillumination.

Figures

Fig. 1

NIR reflectance contrast values vs. measured lesion depth from PLM histology. Blue circles and the blue regression line represent contrast values from the traditional (sound) method. Black (X) symbols and the black regression line represent contrast values from the automated (total) method. Both regressions are statistically significant (P

Fig. 2

NIR transillumination contrast vs. measured lesion depth acquired from PLM histology. Blue circles represent contrast values from the traditional (sound) method. Black (X) symbols represent contrast values from the automated (total) method. Red boxes represent values from the occlusal method. Individual regression calculations showed no statistical significance (P>0.05).

Fig. 3

NIR reflectance and transillumination lesion widths vs. measured lesion depth from PLM histology. Blue circles represent reflectance measurements. Black (X) symbols represent transillumination measurements. Both regressions are statistically significant (P