Thought I'd post an update. After getting Mimi's teeth done for the first time on Oct 7, she lost a bit of weight immediately afterward, then appeared to be doing a bit better, but not really gaining any weight. I found the tip to cut up the hay/grass very helpful - she could eat small pieces but not nip the bigger ones. She did seem to get perkier. Then we had her teeth done a second time (Dr. Legendre said he planed the teeth down to the gum the first time but anticipated a second treatment was necessary) which we did Nov 5th. She hadn't gained any weight by that treatment and I was feeding her critical care. After the second treatment she lost more weight, at one point dipping below 600g (she was 630g when we had her teeth done the second time). I was really despairing. However, after a couple of weeks her manner was definitely far perkier and she was back to her squeaky self and seemed to have more energy, even if she wasn't gaining weight. I continued to give her critical care but she seemed to eat less 'real food' when I did so I tried not to give her too much because I wanted her eating on her own. Following Dr. Legendre's instructions we've stopped pellets (I gave her pellets still after her first tooth treatment just because I was desperate for her to eat and it seemed that was what she would eat), and only feed her hay, grass, plus give her veggies and fruit as treats. After a few weeks of her still not really gaining any weight (and despair on my part) there seemed to be a shift and she started gaining, and as of today she's 874g! I know, still small for a guinea pig, but when we adopted her a couple of years ago she was only 838g (and her previous owners didn't feed her any hay) so she's now the heaviest she's been since we've had her. She squeaks like mad and eats constantly. I've very happy and I hope it continues! Obviously we don't know the long-term prognosis, but I thought I'd post it because relative to some other stories about malocclusion she seems to be doing fairly well. FYI I bought a chin sling but I couldn't figure out how to use it properly. She's a silkie and her hair seemed to be a problem, and trimming it didn't seem to help. Next time we see Dr. Legendre I'll ask him about it.