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Incipient white spot lesions fluoresce less when dry. This may be related to increased light scattering by the lesion, both effects being related to properties of the lesion body and lesion surface layer. To investigate this, extracted premolars with 12 white spot lesions were used. Except when being measured, teeth were stored in humid atmosphere with some thymol. Fluorescence loss was determined with quantitative light-induced fluorescence (QLF) [de Josselin de Jong et al.: Caries Res 1995;29:2-7]; the distribution of scattering-caused paths of returned light (Ï = 1,300 nm) was determined with optical pathlength spectroscopy (OPS) [Popescu et al.: Opt Lett 1999;24: 442-444]. Both measurements were done at the same spot during 20 min in room atmosphere after removal from water. Finally, slices were prepared and transversal microradiography performed to determine lesion depth, mineral loss, surface layer mineral content and thickness. As reported elsewhere, the average optical pathlength in wet lesions did not correlate with fluorescence loss (r = 0.1). However, the variance of the pathlength distribution, indicating the inhomogeneity of the volume wherein the light travels, did (r = 0.77). This indicates that this volume becomes more inhomogeneous with increasing lesion severity. The difference between wet and dry values of pathlength variance correlates with mineral loss (r = 0.85); other optical parameters correlate weakly. Initial speed of change in pathlength parameters did not correlate with penetrability of the lesion surface (when present). Initial speed of change of fluorescence did (r = 0.79). In conclusion: (1) these light paths extend beyond such lesions; (2) the earlier conclusion that fluorescence loss in lesions is not determined by the average light pathlength in the lesion is supported. Probably, such loss is determined by shielding of dentine fluorescence by the lesion. |