My 2.5yo rescue cat has red gums and has lost a few teeth due to this. His teeth appear clean but he has bad breath.
I took him to the vet twice. He's been given some toothpaste to lick on his paw. Apparently as his teeth are clean a dental is pointless according to the vet. Vet said he'll see cat again in a month and may give antibiotics ie steroids but they are a temporary fix, he thinks he'll have gum problems for life and will lose more teeth 
I'm going to take him to another vet as this one doesn't seem very interested, I'd rather treat my cat than wait for his teeth to fall out!
He's negative for fiv and aids and leukaemia. What treatment may help him?!