I literally JUST went through the same thing with Holland!! She had almost all her teeth extracted less than two weeks ago. Same on the meds - she had 2 doses of Buprenex a day for 5 days (hers was oral though, which was not fun, but I can't imagine having to give her a shot!).
Just keep an eye on him, make sure he's eating, drinking and pooping like normal. I found Holland's stools to be looser (not diarrhea) but she went from an all dry food diet to an all wet food diet overnight. For the past few days, Holland has been doing a lot of biting at the air and stretching her jaw. I talked to her vet about it and he was confident that it was just her stitches itching her. He said the most important thing is that she's eating, which she is doing like a champ. And she will let me touch her mouth now; before the extraction she wouldn't let me NEAR her mouth without freaking out.
Holland had her surgery done last Monday (two Mondays ago) and this evening was the first time she's had a real burst of energy. My cat is normally not a big "player", but she's been running around here like crazy, playing with her toys and just being goofy. She had been sleeping a LOT before today - I think it was a mix of post-surgery recovery and just getting used to her "new" mouth.
I think once she's completely healed she will be like a whole new cat, and I'm sure Walli will be the same. I didn't even know Holland had stomatitis (she's not even 2 years old yet) until I found one of her teeth on the floor and then took her to the vet. Poor baby had to have been in SO much pain and I didn't even realize it.
for Walli to feel better soon! I got a lot of comfort from TCS members when Holland had her surgery, I hope you get some comfort here too!
Holland says Thanks! 
), and then the dental trouble on top of that... 
I always tease her about being my special needs child. But really I'm SO glad that I am the one who adopted her because at least I know that she is getting the care that she deserves.
