I asked an insurance man why dental plans weren't integrated into general medical plans. He said that most dental costs were predictable--there wasn't much difference between paying premiums and paying cash--unless you had soft teeth and had to have lots of crowns and whatnot. If you were normal it was a wash.
My experience has been a little different--but I have enough crowns to suggest that my experience isn't average. I wonder what the distribution of costs looks like. Anybody know, or is that proprietary information?