Novel dental dynamic depth profilometric imaging using simultaneous frequency-domain infrared photothermal radiometry and laser luminescence

A high-spatial-resolution dynamic experimental imaging setup, which can pro vide simultaneous measurements of laser-induced frequency-domain infrared p hotothermal radiometric and luminescence signals from defects in teeth, has been developed for the first time. The major findings of this work are (i) radiometric images are complementary to (anticorrelated with) luminescence images, as a result of the nature of the two physical signal generation pr ocesses; (ii) the radiometric amplitude exhibits much superior dynamic (sig nal resolution) range to luminescence in distinguishing between intact and cracked sub-surface structures in the enamel; (iii) the radiometric signal (amplitude and phase) produces dental images with much better defect locali zation, delineation, and resolution; (iv) radiometric images (amplitude and phase) at a fixed modulation frequency are depth profilometric, whereas lu minescence images are not; and (v) luminescence frequency responses from en amel and hydroxyapatite exhibit two relaxation lifetimes, the longer of whi ch (similar to ms) is common to all and is not sensitive to the defect stat e and overall quality of the enamel. Simultaneous radiometric and luminesce nce frequency scans for the purpose of depth profiling were performed and a quantitative theoretical two-lifetime rate model of dental luminescence wa s advanced. (C) 2000 Society of Photo-Optical Instrumentation Engineers. [S 1083-3668(00)00691-8].