Question

I have a four and half year old daughter, and one of her bottom teeth is moving, she did fall the other day and hit her mouth a touch, but nothing drastic to cause her tooth to move?

Answer 

Usually at the age of 5-7 years.
You should have a look at a doctor with your daughter.
I made one experience as a child at about 5. I had a “fight” and hit a teeth of my “rival”, so it seemed he’d fall out. The kindergarden teacher said, that’s not much of a problem, since it was a milktooth and the tooth of next generation should come soon.
The father of this boy was a dentist and he told us all the next day that it can cause problems, if one looses a milktooth too early. Problems, because the first generation prepares the soil for the second and final generation. They are also the placeholders for the second generation.

Peter.