A bear only has 42 teeth?

A bear only has 42 teeth throughout it's lifespan. The only thing I have to ask is... How in the hell did someone get close enough to count the teeth of more than a few bears for the data to be considered fact??? O.O The only thing //I'm// worried about is making sure those teeth don't come down on top of me!!! :D Oh, and for us nerds, bears know the answer to life. 42.