A system and method for using near-infrared or short-wave infrared (SWIR) sources such as lamps, thermal sources, LED's, laser diodes, super-luminescent laser diodes, and super-continuum light sources for early detection of dental caries measure transmission and/or reflectance. In the SWIR wavelength range, solid, intact teeth may have a low reflectance or high transmission with very few spectral features while a carious region exhibits more scattering, so the reflectance increases in amplitude. The spectral dependence of the transmitted or reflected light from the tooth may be used to detect and quantify the degree of caries. Instruments for applying SWIR light to one or more teeth may include a C-clamp design, a mouth guard design, or hand-held devices that may augment other dental tools. The measurement device may communicate with a smart phone or tablet, which may transmit a related signal to the cloud, where additional value-added services are performed.