Man, Dentistry is NOT COMMON.
Britain has a reputation for bad teeth for a reason. (Austin Powers) (He isn't the reason, just a parody/example)
The US has like a whole race of people in the south that can be accused of 'lying through their tooth'. (Rednecks aren't human, right?)
It's not a country thing, or even a money thing. If you happen to notice, some Hollywood stars (Like Harrison Ford, IIRC) have crooked teeth.