Figure 3 A cross section through the fissure system on the occlusal of a bicuspid showing the variation in the depth of the fissure system. From the occlusal the fissure was evenly stained and the existence of the two deep pits was not apparent. Note the translucent zone beneath the two pits – as well as inside the two proximal lesions – demonstrating that the dentine is already responding to the acid demineralisation.