Symptoms of Addison's disease (underactivity of the adrenals) include lethargy, loss of appetite, vomiting, weight loss, diarrhea, shaking, frequent urination, increased thirst... among others.
If your cat has appetite but isn't eating much, it could well be the teeth! I hope so! That would be easier to treat than some of the other possibilities, like Addison's, which can be tricky to control.
It's dangerous for a cat to go too long without eating, so if it
is the teeth, best to get them seen to as soon as possible.