One of my cats licks her chops and and grooms herself obsessively when she has gum inflammation due to whenever her kidneys start functioning poorly. The licking apparently soothes her swollen inflamed (and possibly itchy?) gums. Then we need to make sure she gets more fluids in order to flush the toxins from her kidneys better. After a couple of weeks with more fluid in her diet, her gums improve and she doesn't lick so much. Just one possibility of many.