What you might not know about teeth whiteners
Article Thumbnail ImageFebruary 4, 2010 -- BOSTON - A dizzying array of home teeth-whitening products are on the market, but they differ only slightly. Be it white strips, whitening trays, or paint-on whiteners, whether applied for one hour, two hours, or overnight, they all use the same active ingredients and can achieve the same goal: transforming dingy, discolored teeth into pearly whites.
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But there can be pitfalls on the path to aesthetic nirvana, and dental professionals can help patients avoid them -- if armed with the right information.

Overeager patients can damage their gums, wind up with such searing pain that it hurts to breathe, and even turn their teeth eerily translucent, "kind of like they glow in the dark," said Dorothy Vannah, R.D.H., at the recent Yankee Dental Congress.

Vannah, a professor at Tufts University School of Dental Medicine, helped lead dental practitioners through the thicket of confusion surrounding the billion-dollar-plus whitening industry during a three-hour seminar.

Understanding what's inside these products is key, Vannah said. Only two whitening agents are on the market: carbamide peroxide, most common for home use, and hydrogen peroxide, its stronger counterpart. While hydrogen peroxide is three times stronger than carbamide peroxide, products containing it are not necessarily more potent. That's because whitening products contain varying concentrations of active ingredients.

Focusing on the active ingredient's type and concentration can help dental practitioners determine how patients can best brighten their teeth while minimizing tooth sensitivity.

Sensitivity

And there is almost always tooth sensitivity, Vannah said. While the pain is often mild, she's seen some people in agony after whitening. "They couldn't eat. They couldn't breathe," she said.

That's because of the way that whitening works.

Teeth whitening occurs through an oxidation process, Vannah said. When carbamide peroxide interacts with saliva on the teeth, the chemical decomposes into hydrogen peroxide. That, in turn, degrades into water and oxygen. The oxygen enters enamel and dentin, and diffuses to the areas containing the discolored substances. Essentially, the chemicals "eat the stain and dissolve it," she said.

But if the peroxide enters the dentinal tubules near the nerve space and removes the protective smear layer, teeth can become very sensitive, Vannah said. Patients with wide pulp chambers, especially children, may feel the most pain with whitening. In fact, children don't usually get their teeth bleached, though orthodontists are increasingly bleaching teens' teeth after removing braces.

People with cracks in their teeth aren't usually considered suitable candidates for the cosmetic procedure either.

How to alleviate the pain? Some whiteners with high concentrations of hydrogen peroxide now contain tooth desensitizers, such as potassium nitrate or fluoride, Vannah said. If people use whiteners without desensitizers, they can either decrease the time they bleach their teeth or switch to whiteners with a lower concentration of active ingredients. Another possibility for those using bleaching trays: alternate days of using whitening solution with days of using solutions of potassium nitrate combined with fluoride, she said.

For patients who choose to have their teeth bleached during a one-hour office treatment, hygienists suggest brushing with Colgate's desensitizing PreviDent toothpaste for a full week before the procedure. The in-office treatments utilize up to 35% hydrogen peroxide -- about seven times stronger than the Crest Whitestrips sold in drugstores. "It hurts," one hygienist in the audience said.

In fact, people don't have to put themselves through such pain, Vannah said. With home treatments, whiteners with lower concentrations of active ingredients work just as well as the more potent ones. They just take a little longer.

Typically, when patients use custom-fit whitening trays made by their dentist, they wear the appliances daily during a two-week period. Those who use high-concentration whiteners wear the trays for an hour a day, while those using lower-strength whiteners wear the trays overnight.

Actually, the lower-concentration carbamide peroxide whiteners can be used for just two hours a day, Vannah said. The carbamide peroxide remains active for only two hours, so even if people wear the trays all night long, they get no beneficial effect, she added.

Other side effects

Another potential side effect of teeth whitening is gingival irritation, which "doesn't have to be," Vannah said. Irritation occurs if the whitener gets on the gums. But if whitening trays are trimmed properly, about 1 mm away from the gingival line, then the problem will be less likely to occur.

“If it will stain your clothes, it will stain your teeth.”
— Dorothy Vannah, R.D.H., Tufts
     University School of Dental Medicine

Also, patients need to be taught to put just a small amount of whitener in trays. If any whitener oozes out of the trays onto their gums, patients need to wipe it off immediately.

People with sensitive gums should use either the whitening trays or an alternative product, brush-on peroxide. With the brush-ons, patients simply paint their teeth with the peroxide for one minute, avoiding their gums entirely. "It feels like Super Glue on the teeth," said Vannah, adding that while this method can be quite effective, the products are often hard to find.

Whitestrips can be more problematic, she said. When they are placed on the teeth, they can sit on the gingiva, causing irritation. And if a patient's teeth aren't straight, the strips may not fit properly, thus missing some stains. "It's a real disadvantage," she said.

Not all patients are good candidates for teeth whitening. People with gray stains or lots of restorations on their front teeth don't always get good results. Some people bleach their teeth, then get their restorations replaced to match the color. Otherwise, the restorations "will stick out like neon lights," Vannah said.

Patients who drink lots of alcohol may not get good results either, since bathing the teeth in alcohol can change the enamel, she said. And some dentists now refuse to help smokers whiten their teeth because of fears that the whitening process could increase smokers' risk of oral cancer.

Still, anyone who wants a whiter smile can find a way to try and get one. In addition to home-based products, teeth-whitening kiosks have popped up at malls around the country -- a dangerous development, according to Vannah, because these places rarely have dental professionals involved.

Avoiding overuse

Another issue is overuse. For teens, teeth-whitening products are the most abused products on the market, Vannah said. Teens sometimes bleach their teeth until they turn translucent -- a funky, "really weird look" that can last up to six months, she said. In addition, overbleached teeth can turn brittle.

Sometimes people overbleach teeth because they are dissatisfied with the immediate results. But the true results of bleaching aren't apparent until two days after the whitening process is complete, when the teeth are completely rehydrated.

Patients also need to abstain from drinking coffee, teas, and colas -- or at least drink them with straws -- for at least a few days after bleaching so as not to restain newly whitened teeth, Vannah said.

A good rule of thumb: "If it will stain your clothes, it will stain your teeth," she said.

After that, the pearly white look should last three to five years, Vannah said, though some patients find annual one-weekend touch-ups are enough to preserve their new looks for much longer.

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