Compared with E2, E1 caries penetrate enamel to what extent?

• A. E1 penetrates more than half the enamel thickness
• B. E1 reaches the DEJ
• C. E1 penetrates less than half the enamel thickness
• D. E1 penetrates through enamel into dentin

Answer: (C)

This question tests how deep enamel caries go at different stages. E1 is an early lesion confined to the outer enamel, so its depth is limited to the outer half of the enamel thickness. E2, being deeper, progresses into the inner enamel toward the dentin–enamel junction. Because E1 stays in the outer half, it penetrates less than half the enamel thickness compared with E2. Reaching the DEJ or dentin would require deeper involvement beyond E1.