How to Whiten Your Teeth At Home?

Smiling, which usually feels good, can also make you feel self-conscious if your teeth are less than white or your lips are lined or cracked. But a slew of new treatments and products can keep you from wanting to stifle that grin. Here are the most effective teeth whiteners and brighteners, plus tips on selecting and applying gorgeous and goof-proof shades of red lipstick — just in time for little-black-dress season.

Strips, trays, toothpastes...what really works? Here, our experts reveal their favorites, along with advice on who should see a dentist before considering the DIY approach. Why do teeth change color?

Blame time and your diet. With age, the enamel on teeth becomes thinner and more transparent, and the inner layer, called dentin, looks darker. Teeth also absorb colored liquids throughout your life, says Jeff Golub-Evans, D.D.S., a cosmetic dentist in New York City.

Coffee, tea, cola, and red wine are frequent culprits, along with more tenacious tobacco stains. How do at-home whiteners work? Peroxide is the key ingredient in most whiteners.

This safe-for-the-mouth bleaching agent forms bubbles on enamel that lift away stains. The higher the concentration of peroxide and the longer you leave it on your teeth, the whiter they'll get. The downside: Bleaching molecules can get trapped in nerve passageways, causing increased, though temporary, tooth sensitivity.

Who's a good candidate? "At-home whitening is an option for anyone with a healthy mouth who has been to the dentist in the past year," says Matthew Messina, D.D.S., a consumer adviser for the American Dental Association who practices in Cleveland. Three groups shouldn't do their own whitening: those whose teeth are painfully sensitive to cold; anyone with crowns or fillings on their front teeth (they won't whiten and will end up looking much darker than surrounding teeth); and people whose enamel seems more gray than yellow (due to intrinsic stains from antibiotics like tetracycline taken in childhood).

Assuming your dentist has given you the OK, Dr. Golub-Evans says you can assess your whitening potential this way: Hold a piece of white printer paper next to your teeth. If they look yellow, the stains are probably just on the surface — teeth should turn at least a couple of shades lighter with at-home bleaching. If your teeth look grayish, the discoloration likely lies inside the teeth, and bleaching won't help much.

Your teeth will feel very clean and smooth and even sparkle a little and even look a few shades whiter, but you'll need to repeat this remedy a few times in order to have pearly-white teeth.