Fluorescence radiance loss in enamel following demineralization has been correlated to the amount of mineral lost during the demineralization. The correlation between fluorescence loss measured by Quantitative Light- induced Fluorescence (QLF) and the reflectivity loss measured by an en-face Optical Coherence Tomography (OCT) system was investigated in a demineralization process to produce artificial caries. We used an OCT system which can collect A-scans (reflectivity versus depth graph), B-scans (longitudinal images) and C-scans (en-face images). The power to the sample was 250 (mu) W, wavelength (lambda) =850 nm and the depth resolution in air 16micrometers . Transversal and longitudinal images showed the caries lesion as volumes of reduced reflectivity. A-scans, which show the profile of the reflectivity versus depth of penetration into the tooth tissue, were used for quantitative analysis of the reflectivity loss. Both the fluorescence radiance and reflectivity of the enamel decreased with increasing demineralization time. A linear correlation was observed between the percentage fluorescence loss measured by QLF and the percentage reflectivity loss measured by OCT. It was concluded that the decrease in reflectivity of the enamel during demineralization, measured by OCT, could be related to the amount of mineral lost during the demineralization process.
The average pathlength of light inside dental enamel and incipient lesions is measured and compared, in order to quantitatively confirm the prediction that incipient lesions have higher scattering coefficients that sound enamel. The technique used, called optical pathlength spectroscopy provides experimental access to the pathlength distribution of light inside highly scattering samples. This is desirable for complex biological materials, where current theoretical models are very difficult to apply. To minimize the effects of surface reflections the average pathlength is measured in wet sound enamel and white spots. We obtain values of 367 micrometers and 272 micrometers average pathlength for sound enamel and white spots respectively. We also investigate the differences between open and subsurface lesions, by measuring the change in the pathlength distribution of light as they go from dry to wet.