UCSF

Short wavelength infrared (SWIR) and near-infrared (NIR) imaging methods have been in development for almost two decades for dental use. Due to the high transparency of enamel in the NIR, separate novel imaging configurations such as occlusal transillumination and cross-polarization reflectance imaging have been discovered to be useful in imaging interproximal and occlusal lesions, respectively. Novel clinical probes capable of acquiring simultaneous SWIR reflectance and occlusal transillumination images of lesions on tooth proximal and occlusal surfaces have recently been developed at UCSF. The dual probe is 3D-printed, and the imaging system uses a SWIR camera and fiber-optic light sources that use SWIR light at 1300-nm for occlusal transillumination and SWIR 1450-nm light for reflectance measurements. Previously, this dual probe was used to image extracted teeth with proximal and occlusal lesions, showing promising results verifying false positives using micro-CT images as a gold standard to assess performance. The purpose of this study is to determine the sensitivity and specificity of this novel probe on 40 human test subjects each with 2-4 premolars scheduled for extraction due to orthodontic purposes. In addition to imaging with the dual probe, visible intraoral photos of the teeth were taken prior to extraction. After extraction, radiographs of the teeth were taken, and samples were imaged using microradiography serving as the gold standard. The visible digital images and radiographs were assessed, and all samples were scored with the standardized ICDAS criteria. For the short-wave infrared images, contrast calculations were performed. The sensitivity and specificity were then calculated for visual examination, radiography, individual SWIR reflectance and occlusal transillumination and for combined SWIR reflectance and occlusal transillumination. Our study demonstrates for the first time that near simultaneous transillumination (1300-nm) and reflectance (1600-nm) video can be successfully acquired of lesions in real-time. Both imaging modalities had markedly higher sensitivity for lesions on proximal and occlusal surfaces compared to conventional methods (visual and radiographic images). Reflectance imaging at 1600-nm had significantly higher specificity than transillumination at 1300-nm.