Here's an update…
My attempts at learning to brush Bowpi's teeth kind of failed. I didn't get further than letting her lick the special enzymatic toothpaste off the brush, as opposed to actually getting to her teeth.
Meanwhile, we were able to continue knocking off more plaque with the same regimen of raw meaty bones, dental chews, anti-plaque additives and hard kibble which we'd had going on before. But still, not enough.
Got quotes from a couple more vets, none of which thought her condition urgent either. In the end, we just decided to go with the first vet because I do want to establish a good relationship with a "regular" vet instead of shopping around all the time, and they seem to be good people at this practice.
Bowpi went in for her dental appointment this morning. I felt awful having to rouse her out of deep sleep. She was totally spread out underneath the blanket, taking up the space that I had vacated when I got up in the morning. Dropped her off at 8 AM, got her back about 3 PM.
Total damage, < $500 after Dental Month discounts, no extractions. Yay!
She cried for about twenty minutes straight after we picked her up... poor thing. I had never heard her vocalize quite so much, at least not so continuously. I gave her some anti-anxiety drops in a bit of yogurt, and she settled down. Now she's sleeping off her tough day.
We'll go back in a couple weeks later just to follow up, and they'll try to show me how to brush her teeth. The vet is also supposed to send me some before and after pictures they took of the process, so that should be fun.