Brushing and flossing are everyday ways to keep your teeth bright, white and healthy. Still, if you might feel like your smile is lacking some sparkle or is more yellow than it used to be, you’re not alone.

When the American Academy of Cosmetic Dentistry asked people what they’d most like to improve about their smile, the most common response was whiter teeth. The American Association of Orthodontists also found that nearly 90% of patients requested tooth whitening.

Over time, your teeth can go from white to not-so-bright for a number of reasons. Coffee, tea and red wine are some major staining culprits. What do they have in common? Intense color pigments called chromogens that attach to the white, outer part of your tooth.

Two chemicals found in tobacco create stubborn stains: Tar and nicotine. Tar is naturally dark. Nicotine is colorless until it’s mixed with oxygen. Then, it turns into a yellowish, surface-staining substance.