美国国家公共电台 NPR Navigating The 'Aisle Of Confusion' To Whiten Your Teeth（在线收听）

DAVID GREENE, HOST:

Right from how smells can make us more attractive, let's turn to a multibillion-dollar global industry that is devoted to making you look more attractive, teeth whitening. Just walk into any pharmacy. Go online. You'll see them - toothpastes, gels and strips and paint-on bleaches, all with big promises to give you a bright, white smile. So tell us, NPR's Patti Neighmond, do these things work?

PATTI NEIGHMOND, BYLINE: Not all tooth stains are the same. Some are mostly on the surface of the teeth and come from the food and liquid we consume. Dentist Ruchi Sahota.

RUCHI SAHOTA: Coffee, tea, red wine.

NEIGHMOND: And foods with vibrant, yellow spices, like turmeric or tar and nicotine. Sahota says these surface stains can be reduced with routine brushing, flossing and professional cleaning in the dentist's office. But there are some deeper stains you just can't avoid that come with age and years of chewing.

SAHOTA: The hard, outer shell of the tooth can start to get thinner and start to have these cracks over time.

NEIGHMOND: Literally millions of micro-cracks that can fill up with stain. And the thinner enamel allows the inner core of the tooth to be more visible.

SAHOTA: That inner core of the tooth is more yellow than the white enamel.

NEIGHMOND: This is where bleaching agents come in. They can penetrate that core and turn the tooth whiter again, typically two to seven shades lighter. And that brings us to what some call the dental aisle of confusion.

SAHOTA: Because there are so many options. And you just get confused standing there, trying to figure out which option is the best.

NEIGHMOND: It's not easy. The strips, the gels, the paint-on bleaches aren't regulated by the FDA because it considers them cosmetic. The American Dental Association offers an alternative, an ADA seal of acceptance. Chemist Jamie Spomer directs the program and says, when a manufacturer applies for the seal, an independent panel of dentists analyzes the data and performs studies of their own.

JAMIE SPOMER: The seal is rooted in science. When a consumer sees the ADA seal on a product, it is a symbol that an independent panel reviewed and approved that product for its safety and effectiveness.

NEIGHMOND: Numerous toothpastes carry the ADA seal. But so far, only one over-the-counter bleaching product does. Even so, many of the products that don't carry the seal can be effective, Sahota says, if used as directed. Most will cause tooth sensitivity during the bleaching process and, if you're not careful, other problems as well.

SAHOTA: Oftentimes, the products can leak onto the gums and cause sensitivity. It can basically bleach and blanch the gums.

NEIGHMOND: A safer but more costly option is to go to the dentist's office. A custom-made, take-home tray, which hugs the teeth and ensures the gel's evenly applied, costs around $400. Or have bleach applied in the dentist's office. Gums are protected by rubber, and bleach concentrations are high enough that whitening can occur in just an hour or two. That will cost you around a thousand dollars or more. Patti Neighmond, NPR News.

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