Food and Drinks
Coffee, tea, red wine, cola, berries, and even tomato-based sauces contain pigments (chromogens and tannins) that stick to enamel and stain over time.
Smoking and Tobacco Use
Nicotine and tar in cigarettes and chewing tobacco deeply stain teeth, often giving them a brownish-yellow appearance.
Poor Oral Hygiene
Inadequate brushing and flossing allow plaque and tartar buildup, which can make teeth look discolored.
Aging
