"That cream colored bit is tooth?"
"...that's a lot of tooth."
So the cement held. The tooth apparently is what failed. The tooth is completely dead, so I couldn't feel the fact that it was decaying under the crown, and since it had a metal base, the X-rays couldn't see through it.
So ultimately it was a good thing that it broke, because otherwise my tooth would have become--I quote--"Mushy." And after "mushy" there is not a lot to be done.
Nevertheless, given that crown was over twelve years old, over top of a massive hole, and done on a steep budget by a dentist in Phoenix, I got an amazing run out of it. My dentist saluted her counterpart in the Southwest. (He was trained in India--I mentioned this in passing to my dentist, who said "Aha! I was wondering." Apparently the differences in technique are visible when you're effectively doing a post-mortem on the tooth. She hastened to add that he'd done a very good job, but the technique was substantially different than the way she'd been trained--something to do with the way the little filler dealies in the roots are done and with the base. I had no idea that dentistry differed that way...)
Anyhow, the crown fit so snugly that she had the same problem getting it back on that I did, and wound up having to sand down the top so I wasn't biting weird. I've got an appointment in August for the full removal/recrown/post deal.
"Good news!" she said cheerfully. "It's completely dead so you don't have to get numbed!"
So all's well that ends well, I guess. Until August!