Teeth whitening procedures have effectively restored the smile of people with stained, dull, or discolored teeth. The darker tissue of your teeth, the dentin, can become exposed as the outer layer of enamel is worn away by the effects of aging or things like caffeine and tobacco. Food particles are naturally attracted to a tooth’s enamel by a certain protein. Products like coffee and tea, berries and soy sauce are notorious for staining teeth. Over time, teeth actually become more absorbent and vulnerable to staining from food and other substances. One type of stain—caused by traumatic injuries, medications and fluorosis—actually begins inside the tooth; brushing and flossing don’t help. Another type of stain—one that can be more easily attacked by brushing, flossing and rinsing—is caused by external factors such as foods.