I’m no expert on this. Thought I’d put forward my thoughts though, and bump the thread up.

If you have concerns about her age (Cant believe she’s 9!) you might consider doing some blood work first. This might give indicator of which is best anaesthetic to use. I did come across something about older bunnies having a lesser dose of the injectable anaesthetics as they can take longer to come out of it. Question for your vet as I don’t know how accurate that info is. It may vary drug to drug.

How did she respond to what they gave her last time? If she did well, I think I would choose that again as I can’t imagine it’s easy to continually administer gas via a mask and do dental work. Plus, given it’s been a while, they may need to keep her under a while to tend to any issues.

I had one of my buns undergo op on face recently and learnt they put the rabbits in an oxygen tent afterward to aid recovery. He was quite perky afterward. You might want to ask if they do this. I felt it helped.  

I’d also check about what pain med they send home and how much is given. My boy was less then perky 24hrs afterward, due to inadequate pain relief.  

Do you have any critical care? You could start giving her a little dish of that or pellet mush so she’s getting adequate fibre pre-dental.

Sometimes I’ve added hay I’ve ground down to pellet mush.

My vet always puts my buns completely under. Bindi is almost 9 and always makes out okay. They are only under for a very short amount of time. I always do the pre-anaesthetic bloodwork first.

I know it’s nerve-wracking putting an older bun under. Bindi needs his molars done every 5 months or so.