Quantitative dental measurements by use of simultaneous frequency-domain laser infrared photothermal radiometry and luminescence.

Modulated (frequency-domain) infrared photothermal radiometry (PTR) is used as a dynamic quantitative dental inspection tool complementary to modulated luminescence (LM) to quantify sound enamel or dentin. A dynamic high-spatial-resolution experimental imaging setup, which can provide simultaneous measurements of laser-induced modulated PTR and LM signals from defects in teeth, has been developed. Following optical absorption of laser photons, the experimental setup can monitor simultaneously and independently the nonradiative (optical-to-thermal) energy conversion by infrared PTR and the radiative deexcitation by LM emission. The relaxation lifetimes (tau1, tau2) and optical absorption, scattering, and spectrally averaged infrared emission coefficients (mu(alpha), mu(s), mu(IR)) of enamel are then determined with realistic three-dimensional LM and photothermal models for turbid media followed by multiparameter fits to the data. A quantitative band of values for healthy enamel with respect to these parameters can be generated so as to provide an explicit criterion for the assessment of healthy enamel and, in a future extension, to facilitate the diagnosis of the onset of demineralization in carious enamel.