Cash 
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.