How common is it, really, in the US? I genuinely don't know.
On the one hand, I hear that medical (and thus presumably dental) insurance costs a fortune, and even then the "co-pay" means that many hesitate to seek treatment. I can't imagine that "my teeth aren't as white as I'd like" is something insurance companies like paying for (or rather, they don't like paying for anything, but something purely cosmetic seems easy to deny), so how are people affording this? is it just the wealthy? If I wander around poorer areas, will I start seeing ordinary teeth?