Cone beam computed tomography (CBCT) can provide enhanced information for diagnosing dental diseases when compared to 2D radiographs. However, other nonionizing imaging modes such as near-infrared (NIR) transillumination may have clinical potential to supplement radiographic methods. In a study of 13 extracted human teeth, we compared clinical features between 2D radiograph, CBCT, and near-infrared transillumination imaging. We found that near-infrared imaging independently, and in some cases exclusively, was successful in identifying early demineralization and shallow enamel features, while radiography was optimal for capturing deeper decay and developed caries. We report that near-infrared transillumination imaging is well-suited for rapid screening of patients for detection of early problem sites and as a preliminary assessment tool to guide administration of radiographs.
Why is this work important?
Two-dimensional radiographs and cone beam computed tomography are commonly used for evaluating sub-surface hard structures of teeth. While 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. It is not well understood what clinical features, if any, are present in NIR dental images, especially at 850 nm. Our previous work has examined the sensitivity of 850 nm NIR images to early caries lesions, but if NIR is to synergistically augment X-rays and CBCT as the standard of care, we must evaluate how well such images represent other clinical features.
What are our contributions?
We examine and compare features in multiple extracted teeth using conventional radiographic, CBCT, and NIR transillumination modes. NIR imaging can provide unique diagnostic value, primarily in its ability to reveal the extent of surface demineralization. We also provide examples where NIR illumination indicated underlying problem sites in need of further clinical attention and propose the use of NIR imaging to guide targeted and rational use of ionizing radiation in patients. We also show that NIR imaging identifies clinical features associated with early dimineralization and enamel caries that are not apparent upon expert visual examination.
What are the next steps?
Ongoing work is being done to model the interaction of light inside the tooth in order to provide even more diagnostic power.