Ouch! Poor kitty! Try giving him Colloidal Silver as his drinking water - it kills infections and is good for many issues in their bodies. However, I would measure it when you put it out and monitor consumption to see that he's not going on a drinking strike. If he doesn't drink it, you'll be faced with dehydration and that's worse. So put out some good "CS" (from health food stores) and watch his consumption or lack of it. If he won't drink it, try putting some in his water (not straight up CS, but part), then increase it gradually. IF he'll drink it straight up, his dental infection will clear up quicker, and many times they actually seem to know it will help them and they drink it on their own. Hope it works, he's in pain and soon will quit eating entirely. Keep us posted?
May Christ be in your heart and life!