Measurement of the Depth of Lesions on Proximal Surfaces with SWIR Multispectral Transillumination and Reflectance Imaging

Yihua Zhu,Daniel Fried

doi:10.3390/diagnostics12030597

Abstract

The aim of this study was to compare the diagnostic performance of dual short-wavelength infrared (SWIR) transillumination and reflectance multispectral imaging devices for imaging interproximal lesions with radiography using extracted teeth that had been imaged with micro-computed tomography (microCT). Thirty-six extracted teeth with 67 lesions on the proximal surfaces were imaged using a newly fabricated SWIR multispectral proximal transillumination and reflectance imaging device along with an existing SWIR multispectral occlusal transillumination and reflectance device. The ability of SWIR imaging and radiography to detect lesions and accurately assess lesion dimensions were compared using microCT as a standard. Occlusal and proximal transillumination and occlusal reflectance performed best for imaging interproximal lesions while proximal reflectance was not useful for imaging interproximal lesions from tooth buccal and lingual surfaces. There was high correlation of the lesion dimensions measured in occlusal and proximal transillumination images compared to microCT and moderate correlation in occlusal reflectance images. The correlation between the lesion depth measured in radiographs and the lesion depth measured with microCT was not significant. This study demonstrates that SWIR occlusal and proximal transillumination and SWIR occlusal reflectance images are useful for imaging interproximal lesions and they provide more accurate measurements of lesion severity.

Highlights

Short wavelength infrared (SWIR) and near-IR imaging (NIR) methods have been under development for almost 20 years for use in dentistry and several NIR clinical devices are available commercially
The lesion contrast was high for most proximal transillumination images, only seven of the lesions were visible in the proximal reflectance images of the and lingual
45 of the 67 interproximal lesions were visible in occlusal reflectance images and the mean contrast of those lesions was According to this study and three other studies, proximal and occlusal transillumination imaging and occlusal reflectance imaging performed as well or significantly better than radiography for the detection of lesions on proximal surfaces [2,9,28]

Summary

Introduction

Short wavelength infrared (SWIR) and near-IR imaging (NIR) methods have been under development for almost 20 years for use in dentistry and several NIR clinical devices are available commercially. Due to the high transparency of enamel at longer wavelengths, multiple imaging configurations are feasible, caries lesions can be imaged using transillumination and reflectance from tooth occlusal, buccal and lingual surfaces [1,2]. The positions can be alternated to get images of each surface since this method will have greater sensitivity for those lesions located closer to the detector. This is the same imaging geometry used to acquire bitewing radiographs. Interproximal lesions, the lesions located at the proximal contact points in between teeth, can be imaged via all three imaging geometries. Transillumination of the proximal contact points between teeth can be accomplished via occlusal transillumination by directing

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