My dog has a hard lump inside her cheek?

the lump is about the size of half a golf ball, but it swells quiet often to a larger size and causes the face 2 swell on that side, i have taken her 2 the vets and she has had an x ray as initially we all thought the lump was bone because its so hard, turned out its not, she then had a ultrasound and a needle in the lump 2 take fluid, the tests came back that the fluid was infectious matter, so my dog has had a 2 week course of antibiotics which stopped the swelling and made the lump seem smaller and a little softer, so we then carried on with another 2 weeks course of antibiotics which she finished yesterday today the face is the same as it was at the start, swollen! the vet seems 2 think that maybe she has an abscess inside a pocket in the face which may never go away! her teeth have been checked and there all fine, but surly my dog can't go round with a massive face all the time! the lump or her face don't hurt her at all, and she eats and drinks fine and there is no change in her personality, so i was just wondering if any one has ever had similar problems or could maybe give your opinions,