Why? Dental work is not covered by the government here in Canada, and even private insurance caps usually have a very low amount that they cover (1-2k$ per year no matter how bad your teeth are, and a single root can treatment can put you over that limit very quickly). So it really has nothing to do with it being American and I think dentistry in general can have a problem when it comes to treatment necessity, over diagnosis and fixing things that may not need fixing.

Now that I think about it, I've actually rarely heard anything about single payer dental coverage, which is weird considering just how important dental health to life quality. Is dental work free in countries like Germany, the NL, Sweden etc?

In Norway, most health services are funded by the authorities.

The notable exception being dentistry. The dentists (mostly) fight tooth and nail not to be publicly funded; the reason, of course being that the state holds way more leverage than individuals - and rates are sure to plummet once the state foots the bill.

If I go to see my doctor, am admitted to hospital or whatever, I pay a small deductible - $20-40 - each time; once my expenses in a calendar year exceeds approx. $300, I get a waiver valid for the rest of the year, capping my direct medical expenses (excluding dentistry) at $300 a year.

For comparison, last time I had a tooth filled a few years ago, my dentist charged me $300 for a 20 minute job.

Dentists outside the USA do this, too. I once had a dentist outside the US even admit this to me. She seemed embarassed by her former classmates from dental school who were operating this way.