Aw, poor boy. I know that certain antibiotics are used for different illnesses but I'm wondering if your vet can give him an injection of Convenia. It's an antibiotic that works for two weeks and you don't have to worry about pilling him or squirting a liquid down his throat. It works pretty fast, too. I'm not sure if it would apply in this case but it might be something to ask your vet about. Both my Pidge and Coco Puff had the shots and it really worked fast for them but then again it wasn't for dental.