Periodontal disease, tooth resorption, inflammation of the mouth and fractured teeth can all be painful. A cat with a sore mouth may drop food, chew on one side, choose soft food, drool or become less interested in grooming. Bad breath is also common with several mouth diseases.
It is hard to assess every tooth in an awake cat. A full dental examination is therefore often done under anaesthesia, where each tooth can be probed and dental X-rays can show changes below the gum line. This matters because very painful dental disease can be invisible in a quick look in the mouth.
Book a dental assessment if your cat changes the way it eats, drools, has bad breath or reacts when its face is touched. A cat that stops eating completely or gets facial swelling should be examined urgently.