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How Do Teeth Whiteners Work?

Tooth whitening is an $11 billion industry in the U.S., with products used by more than 12 percent of American households every year. We’re definitely shelling out for whiter teeth—but are we getting them?

Sort of. As the video above from the American Chemical Society explains, whitening products vary in effectiveness. Nearly all commercial products—from the treatments administered by dentists to at-home whitening strips and mouthwashes—include hydrogen peroxide. The efficacy of these products depends on three things: how long they stay on your teeth, how concentrated they are, and the source of the discoloration on your teeth. If you use a concentrated product as it’s meant to be used, you will likely see a brightening effect.

Unfortunately, this effect is temporary. "Once you stop with the bleach, it regresses—your teeth start returning to their original color," American Society for Dental Aesthetics president Irwin Smigel told Prevention. "Very few people are happy with the color once it starts regressing, so they'll do teeth whitening again and again."

Also, these products are not intended for long-term use. They’re mostly safe in small doses, but over time, soaking your teeth in a bleaching agent can hurt your gums and teeth.

"Ten years ago, people weren't even aware of bleaching," Smigel said. "Now every dentist I know has had to cut off at least one patient because of overbleaching. People come in with great, great pain, and I can see immediately from the color of their teeth and the irritation along the gums that they've been bleaching and bleaching."

If a lifetime of bleaching is off the table, what about all those “natural” whitening remedies you see online? Dentists agree that baking soda is safe as long as you also brush your teeth with toothpaste, but it can only scrub your teeth, not brighten them.

And then there are the fruit remedies recently touted by Dr. Oz, who declared that brushing with a mixture of strawberries and baking soda can whiten teeth. Do not do this. Scientists tested the mixture on extracted human teeth and declared it a real dud. Not only does the strawberry/baking soda combo not brighten teeth, but it actually hurts them. A naturally occurring strawberry compound called malic acid eats away at teeth’s enamel, making them softer.

If white teeth are important to you, there are two things that will always help: regular brushing and flossing. 

Image from YouTube // American Chemical Society

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Big Questions
Why Does Turkey Make You Tired?
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Why do people have such a hard time staying awake after Thanksgiving dinner? Most people blame tryptophan, but that's not really the main culprit. And what is tryptophan, anyway?

Tryptophan is an amino acid that the body uses in the processes of making vitamin B3 and serotonin, a neurotransmitter that helps regulate sleep. It can't be produced by our bodies, so we need to get it through our diet. From which foods, exactly? Turkey, of course, but also other meats, chocolate, bananas, mangoes, dairy products, eggs, chickpeas, peanuts, and a slew of other foods. Some of these foods, like cheddar cheese, have more tryptophan per gram than turkey. Tryptophan doesn't have much of an impact unless it's taken on an empty stomach and in an amount larger than what we're getting from our drumstick. So why does turkey get the rap as a one-way ticket to a nap?

The urge to snooze is more the fault of the average Thanksgiving meal and all the food and booze that go with it. Here are a few things that play into the nap factor:

Fats: That turkey skin is delicious, but fats take a lot of energy to digest, so the body redirects blood to the digestive system. Reduced blood flow in the rest of the body means reduced energy.

Alcohol: What Homer Simpson called the cause of—and solution to—all of life's problems is also a central nervous system depressant.

Overeating: Same deal as fats. It takes a lot of energy to digest a big feast (the average Thanksgiving meal contains 3000 calories and 229 grams of fat), so blood is sent to the digestive process system, leaving the brain a little tired.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Big Questions
How Are Balloons Chosen for the Macy's Thanksgiving Day Parade?
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The balloons for this year's Macy’s Thanksgiving Day Parade range from the classics like Charlie Brown to more modern characters who have debuted in the past few years, including The Elf On The Shelf. New to the parade this year are Olaf from Disney's Frozen and Chase from Paw Patrol. But how does the retail giant choose which characters will appear in the lineup?

Balloon characters are chosen in different ways. For example, in 2011, Macy’s requested B. Boy after parade organizers saw the Tim Burton retrospective at the Museum of Modern Art. (The company had been adding a series of art balloons to the parade lineup since 2005, which it called the Blue Sky Gallery.) When it comes to commercial balloons, though, it appears to be all about the Benjamins.

First-time balloons cost at least $190,000—this covers admission into the parade and the cost of balloon construction. After the initial year, companies can expect to pay Macy’s about $90,000 to get a character into the parade lineup. If you consider that the balloons are out for only an hour or so, that’s about $1500 a minute.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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