Late secondary molars?

[floppops]

My DD is 2.8 years old. She is now getting one of her secondary molars so only has 17 teeth.
Isn't that quite late?
Have only just realised why she is so cranky and throwing her toothbrush across the room with rage!
Should I be worried? Are they supposed to have 20 teeth by now?

depends when she started getting teeth. If she was late starting she will be a bit later finishing. I think they normally have 20 milk teeth by the time they are 3 (on average)