Figure 4 shows an arrested lesion located in a fissure. The color image in Fig. 4A shows that the lesion area is highly pigmented and appears much darker than the surrounding tooth structure. The microCT image in Fig. 4B shows a fairly large lesion that penetrates to the underlying dentin. There is a highly mineralized surface zone that is much lighter than the lesion body and appears as light as the surrounding sound enamel. The line profile of density vs position extracted at the position of the yellow line shows that the mineral content of the surface zone located at the position of the red arrow approaches that of sound enamel (3.0 g/cm3).