Your teeth can get stained when dark foods (such as beets and berries), drinks (think colas and tea), or substances in cigarette smoke stick to plaque or tartar on the surface of your teeth.
Such substances can also seep into tooth enamel, Gerard Kugel, DMD, says. Your tooth enamel also thins with age, exposing the yellowish surface (called dentin) underneath.
Choosing a Tooth Whitener
Getting your teeth professionally whitened, under the care of your dentist, is the most effective way to whiten your smile. But you can also do it at home.
If you decide to try it on your own, Kugel recommends looking for a product with hydrogen or carbamide peroxide, both of which penetrate tooth enamel and lighten stains. He finds strips and trays to be the most effective for overall whitening. That's because real results, he says, depend on a higher concentration of peroxide and how long it's on the teeth.
However, whitening this way could make your teeth more sensitive, Kugel says. If so, he suggests using whitening products only every other day or use sensitive-formula toothpaste.
Drugstore trays aren't customized to your bite, so they can put some peroxide on your gums. This can be irritating but doesn't appear to be harmful, Kugel says. He finds over-the-counter strips are better at placing peroxide squarely on the teeth.
Whitening may backfire if you have visible bonding or fillings. They're matched to your teeth and can't be lightened by peroxide. Thus the downside of DIY whiteners - their lack of speed - is also a plus: "If you go slow, you can whiten your teeth just enough, " Kugel says.
Other Whitening Products for Home
What about other drugstore products that say "whitening" on the label? Kugel gives the lowdown:
Brushing it off. Whitening toothpastes have mild abrasives that remove superficial stains trapped in plaque, taking you a few shades lighter but very slowly.
Getting liquid. Mouthwashes are better for fresh breath; they have low levels of peroxide and are on teeth only for the seconds it takes to swish. You won't get much, if any, whitening action.
Stringing it along. Floss might attack between-teeth stains, but "there is very little data about whether it whitens teeth, " Kugel says. "It's just cleaning your teeth well, " which, nevertheless, is always a good thing.
Gerard Kugel, DMD, professor of prosthodontics and operative dentistry, Tufts University School of Dental Medicine, Boston.