Periodontal disease begins when bacteria in the mouth form a substance called plaque that sticks to the surface of the teeth. Minerals in the saliva then harden the plaque into dental tartar (calculus). While tartar above the gum line may be visible, it is not the primary cause of disease. Disease occurs when bacteria in the plaque and tartar spread below the gum line and into the bloodstream. Without treatment, periodontal disease can lead to heart, lung, kidney disease, and a shortened lifespan for your pet.1 By the time they turn three years old, most dogs and cats have signs of periodontal disease.1