That's the stage when individuals usually experience pain, although pain can also occur when the caries lesion involves the dentin layer since sensory nerve fibers travel through tubules in the dentin.

在这个阶段，患者常会感到疼痛，但牙本质层受累产生龋坏时也可能有疼痛产生，因为感觉神经也分布在牙本质的管道中。