If youre quaffing red wine and black tea, or smoking cigarettes or cigars, expect the results to show up as not-so-pearly whites. Other culprits to blame for dingy teeth include colas, gravies, and dark juices. Bottom line: If its dark before you put it in your mouth, it will probably stain your teeth. Brush immediately after eating or drinking foods that stain teeth and use a good bleaching agent, either over-the-counter or in the dentists office. For convenient teeth-cleaning action, eat an apple.