Dual short wavelength infrared transillumination/reflectance mode imaging for caries detection.

We have developed a clinical probe capable of acquiring near-simultaneous short-wavelength infrared (SWIR) reflectance and occlusal transillumination images of lesions on tooth proximal and occlusal surfaces. We hypothesize that dual images will aid in differentiating between shallow and deep occlusal lesions and reduce the potential of false positives (FPs). The aim of this study was to test the performance of the dual reflectance and occlusal transillumination probe on extracted teeth prior to commencing clinical studies. The dual probe was 3D printed and the imaging system uses an InGaAs camera and broadband superluminescent diode light sources that emit broadband light at 1300 nm for occlusal transillumination and 1600-nm light for cross-polarization reflectance. The diagnostic performance of the dual probe was assessed using 120 extracted teeth with approximal and occlusal lesions. Reflectance and transillumination images were fused into single images to enhance the contrast between sound and lesion areas. The lesion contrast in both modes did not increase significantly with either the lesion depth or the distance from the occlusal surface for approximal lesions. In addition, the diagnostic performance of radiography, the individual reflectance and transillumination images, dual images, and fused images were compared using micro-computed tomography as the gold standard. Reflectance imaging at 1600 nm yielded the highest diagnostic accuracy for lesions on both occlusal and proximal surfaces while radiography yielded the lowest number of FPs. This study demonstrates that simultaneous acquisition of both reflectance and transillumination SWIR images is possible with a single clinical device.