Dental plaque is a sticky layer of bacteria that accumulate on the teeth, including where the toothbrush can not reach. Many foods you eat can cause bacteria in your mouth to produce sourness. Sugary foods are a significant source of plaque, but others may not be aware of the damage. Starch, such as bread, cookies and cereal, also causes acid formation. Plaques also produce substances that stimulate the gums, turning them red, sensitive and prone to bleeding. This can cause gum disease, gums that come off the teeth and form pockets full of bacteria and pus. If you do not treat the gums, the bones around the tooth may be damaged, the teeth may become loose or must be removed.