Fig. 5.

Contrast between smooth surface erosion and sound enamel for various illuminating wavelengths and acid exposure times. Top left: 6 h, pH 3 exposure. Top right: 4 h, pH 3 exposure. Bottom left: 2 h, pH 3. Bottom right: 1 h, pH 3. For all four panes: (a) 405-nm reflected image; (b) 444-nm reflected image; (c) 532-nm reflected image; (d) 635-nm reflected image, and (e) 405-nm illuminated AF image. Mean and standard deviation of measured contrast for each imaging modality are shown in the plots. Blue line in each image indicates location where contrast was measured.