title: Thermophotonic lock-in imaging of early demineralized and carious lesions in human teeth.
abstract: As an extension of frequency-domain photothermal radiometry, a novel dental-imaging modality, thermophotonic lock-in imaging (TPLI), is introduced. This methodology uses photothermal wave principles and is capable of detecting early carious lesions and cracks on occlusal and approximal surfaces as well as early caries induced by artificial demineralizing solutions. The increased light scattering and absorption within early carious lesions increases the thermal-wave amplitude and shifts the thermal-wave centroid, producing contrast between the carious lesion and the intact enamel in both amplitude and phase images. Samples with artificial and natural occlusal and approximal caries were examined in this study. Thermophotonic effective detection depth is controlled by the modulation frequency according to the well-known concept of thermal diffusion length. TPLI phase images are emissivity normalized and therefore insensitive to the presence of stains. Amplitude images, on the other hand, provide integrated information from deeper enamel regions. It is concluded that the results of our noninvasive, noncontacting imaging methodology exhibit higher sensitivity to very early demineralization than dental radiographs and are in agreement with the destructive transverse microradiography mineral density profiles.
authors.affiliation: University of Toronto, Department of Mechanical and Industrial Engineering, Center for Advanced Diffusion-Wave Technologies, 5 King's College Road, Toronto, Ontario, M5S 3G8, Toronto, Canada.
authors.forename: Nima
authors.initials: N
authors.lastname: Tabatabaei
authors.forename: Andreas
authors.initials: A
authors.lastname: Mandelis
authors.forename: Bennett Tochukwu
authors.initials: BT
authors.lastname: Amaechi
mesh_terms: D003731:Dental Caries / Q000175:diagnosis* / Q000000981:diagnostic imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008852:Microradiography; D055096:Optical Devices; D055620:Optical Phenomena; D011861:Radiography, Dental; D011874:Radiometry / Q000295:instrumentation / Q000379:methods; D017001:Tooth Demineralization / Q000175:diagnosis* / Q000000981:diagnostic imaging