Brushing and flossing help control the plaque and bacteria that cause dental disease. Plaque is a film of food debris, bacteria, and saliva that sticks to the teeth and gums. The bacteria in plaque convert certain food particles into acids that cause tooth decay. Also, if plaque is not removed, it turns into calculus (tartar). If plaque and calculus are not removed, they begin to destroy the gums and bone, causing periodontal (gum) disease.