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Three differently fluorescing zones in carious dentin have been described [Lennon et al., Caries Res 2001;35:265]. The central orange-red fluorescing zone appears to correspond to the zone of penetration and can be successfully used as an indicator for infected dentin [Lennon and Buchalla, Caries Res 2002;36:315-319). However, the relationship of the more superficial, intensely fluorescing bright green zone and the outer dark zone to the established histological zones in dentin caries has not yet been shown. The aim of this study was to investigate the mineral content of these fluorescent zones in carious dentin. Teeth with dentin caries were sectioned and a 100 µm thick slice was prepared from the cut surface using a hard tissue microtome. The thin slices were excited using violet light (370- 420 nm) from a 35 W xenon discharge lamp. The fluorescence produced by the samples was observed through a 530 nm highpass filter and photographed using a digital camera. Microradiographs of each slice were exposed to CuK á X-rays, 20 kV, 30 mA for 130 min at a focal distance of 24 cm. The microradiographs were digitized and thresholded to isolate both hypermineralized and hypomineralized areas of each sample. The colors of the hypermineralized and hypomineralized masks were converted to green and red, respectively, and then converted to an outline. The outlines indicating the areas of hypermineralization and hypomineralization were superimposed on the fluorescence image of the samples using Adobe PhotoShop. Both the central orange-red fluorescing zone and the bright green fluorescing zone were hypomineralized. The outermost dark zone was hypermineralized. It can be concluded that the recently described differently fluorescing zones in carious dentin correspond to zones of hypermineralization and hypomineralization. |