2-D radiographs, while commonly used for evaluating sub-surface hard structures of teeth, have low sensitivity for early caries lesions, particularly those on tooth occlusal surfaces. Radiographs are also frequently refused by patients over safety concerns. Translucency of teeth in the near-infrared (NIR) range offers a non-ionizing and safe approach to detect dental caries. We report the construction of an NIR (850 nm) LED imaging system, comprised of an NIR source and an intraoral camera for rapid dental evaluations. The NIR system was used to image teeth of ten consenting human subjects and successfully detected secondary, amalgam–occluded and early caries lesions without supplementary image processing. The camera-wand system was also capable of revealing demineralized areas, deep and superficial cracks, and other clinical features of teeth usually visualized by X-rays. The NIR system’s clinical utility, simplistic design, low cost, and user friendliness make it an effective dental caries screening technology in conjunction or in place of radiographs.
Why is this work important?
While two-dimensional radiographs are the current standard of care for diagnostic dental imaging, they have low sensitivity for early caries lesions, particularly those on tooth occlusal surfaces. They are also frequently refused by patients over safety concerns about exposure to ionizing radiation. Medical image acquisition without ionizing radiation can expand the use of important diagnostic tools and decrease safety concerns.
What has been done before?
NIR light can be transmitted across healthy dental enamel with marginal scattering, allowing for imaging dental features. Much previous work has focused on light at 1310 nm, which strikes a balance between enamel and water attenuation, but such a wavelength often requires expensive sensors to image. NIR light at 850 nm has similar dental imaging properties, but it has not been studied as thoroughly as NIR at 1310 nm. Previous studies have similarly neglected the extent to which indicators of dental health, especially early caries associated with the onset of more severe conditions, can be identified in 850 nm NIR images.
What are our contributions?
We describe the construction of a near-infrared imaging device to identify dental caries without the use of radiographs. Light-emitting diodes at 850 nm allow for the use of a low-cost imaging sensor. Its camera-wand design allows for multiple imaging configurations: reflectance, transillumination, and occlusal transillumination. We validate the diagnostic uses for the images produced by our device, determining that they provide insight into the location of caries without ionizing radiation. The camera-wand system was also capable of revealing demineralized areas, deep and superficial cracks, and other clinical features of teeth usually only visualized by X-rays.
What are the next steps?
Ongoing work is being done to analyze the extent of features made visible by our device and to model the interaction of light inside teeth in order to provide even more diagnostic power.