(TH) Healthy Teeth = Happy Cats. Oral disease and infection is common in cats of all ages, although it is more common in cats 7 years and older. If left untreated, the infection can lead to gum disease, tooth decay and tooth loss. The infection can spread through the bloodstream to cause kidney, liver, lung and heart disease.Common signs of oral disease are: yellow-brown tartar near the gum line; red, swollen or bleeding gums, persistent bad breath, abnormal drooling, pawing at the mouth, loose or missing teeth, difficulty eating, and loss of appetite.