Which statement is true about mice in the age range of 11 to 14 days?

• A. Teeth erupt at day 7
• B. Teeth are beginning to erupt at day 11
• C. Teeth erupt at day 21
• D. Teeth erupt at day 30

Answer: (B)

In neonatal mice, dental development is timed so you can use tooth eruption as a developmental marker. The first incisors begin to push through the gums around the second week of life. So, within the 11 to 14 day window, you’d expect to see the very beginnings of eruption—tiny incisors just starting to emerge at the front of the mouth. That’s why the statement about teeth beginning to erupt at day 11 is the best fit for this age range.

If you look earlier than this window, you wouldn’t expect visible eruption yet, since the teeth haven’t broken through the gingiva. If you’re looking at much later ages (like day 21 or day 30), you’d see more advanced eruption and wider dental development, which isn’t characteristic of the 11–14 day stage.