Teeth Whitening: What Works, What Doesn’t

Boston Globe—Despite a sagging stock market, looming budget cuts, and troops massing for war, smiles these days seem brighter than ever. And why not? As self-improvement plans go, whitening teeth is faster than losing weight, easier than exercising, and safer than plastic surgery.

The American Academy of Cosmetic Dentistry estimates that between 1996 and 2000 consumer demand for whitening procedures grew more than 300 percent. In the last decade, whitening has become available in 90 percent of US dental practices. Two years ago, Crest White strips became one of the most successful oral product launches ever when it earned $200 million for Procter &Gamble in its first 12 months on the market.

“Now people actually want to see the dentist,” said John Bardwell, head of the aesthetic dentistry department at Tufts School of Dental Medicine. “It’s a simple procedure. It makes people look better, and everyone wants to look good.”

Teeth whitening refers to procedures and products that temporarily bleach teeth, which darken naturally with age. Peroxide- containing products work through a tooth’s translucent enamel surface to change the color of the dentin underneath, probably by oxidizing, or getting rid of, organic compounds that stain the tooth. It takes about a half-hour to two hours, depending on the concentration of peroxide. Whitening toothpastes, paint-on whiteners, floss, mouthwashes, and chewing gums generally don’t have sufficient contact time or concentration for effective color change, said Dr. Robert Gerlach, principal scientist for worldwide clinical investigations at Procter and Gamble.

The strongest whiteners – with the fastest results and highest prices – are administered in dentist offices or teeth-whitening boutiques. Gels containing 15 to 35 percent hydrogen peroxide (or the carbamide peroxide equivalent, a number three times higher) are squirted into custom-fitted mouth trays for a half hour or so. The price can run about $500 to $600, and often includes take-home touch- ups. Many of the franchised systems – BriteSmile, Zoom, and others – tout lights that supposedly activate the peroxide gel for even greater whitening power. In studies, however, the lights have been shown not to bleach teeth any whiter than the gel alone, said Dr. Gerard Kugel, associate dean for research at the Tufts University School of Dental Medicine.

Dentists also sell products for home use – for more-gradual results and touch-ups – usually containing about 3 to 7 percent hydrogen peroxide (most often as 10 to 22 percent carbamide peroxide). The cost is about $400 to $600. The slower-release carbamide peroxide only works during the first two hours, but people still wear trays overnight: “It’s hard to sit around with a tray in your mouth for two waking hours,” Kugel said.

“If you’re getting married on Saturday, you might opt to get bleached at the dentist,” said Richard Niederman, director of the Center for Evidence-Based Dentistry at the Forsyth Institute and associate professor at Boston University’s Henry M. Goldman School of Graduate Dentistry. “If you’re going to the prom in a month, a home system may be as effective.”

Some of the vast array of products in the local drug store or on the Internet may be as safe and effective as those from the dentist, but labels do not always list the concentration of peroxide or the concentration of potentially harmful ingredients, such as phosphoric or citric acid, which make teeth appear whiter by etching and possibly damaging the enamel surface. With the exception of the well- studied Crest Whitestrips, most products on the consumer market do not have scientifically credible safety and effectiveness studies, and federal regulations don’t mandate safe or effective cosmetic products.

But whitening may not even work as well as the most rigorous studies suggest. Three years ago, in a systematic review of hundreds of studies of the available dentist-prescribed, at-home whitening gels used in mouth trays, Niederman and his colleagues found only seven that met the highest standards (randomized trials with placebo control groups). Pooled together, 73 percent of people had noticeable teeth whitening due to the whitening products. A remarkable 20 percent of people in the placebo groups also showed noticeably whiter teeth, which may be due to study participants being more conscientious about healthy behaviors, such as brushing better, Niederman said. Also, based on this study, about half of people using whitening products will need retreatment to maintain their whitened teeth for longer than six months.

One of the most common problems with whitening seems to be tooth sensitivity, which usually goes away soon after treatment. Dentists speculate that whitening opens up pores in the enamel to the dentin, which in turn surrounds the pulp and nerve, and may make the tooth more vulnerable to heat, cold, and sugar. A high-fluoride toothpaste may help lessen this sensitivity by shoring up the tooth’s enamel.

One spam e-mail pitching a whitening product warns that high doses of hydrogen peroxide in competing products can turn the tongue and other tissues white. That may be true, Kugel said, but the effect is temporary, infrequent, and harmless. The same holds true with peroxide drips on dark complexions. There’s no reason to worry, but rinse off any peroxide on your skin. Overall, he and others recommended using lower-dose products with proven effectiveness documented in published, peer-reviewed studies. Teeth whitening isn’t recommended for people with veneers (thin shells of porcelain), crowns, or reconstructive work, because it may make their teeth whiter than the surrounding material.

“Whitening is probably the safest thing we do in dentistry,” said Kugel, who like all the dentists interviewed for this story, whitens his teeth. “Drinking a cola does more damage to teeth than what we see in bleaching studies.”

(© 2003 Carol Cruzan Morton. All Rights Reserved. Originally published in the Boston Globe. Last known link)

Photo/Caption: Dr. Radford Goto applies a whitening gel to the teeth of a patient at a BriteSmile office in Manhattan. / NEW YORK TIMES PHOTO / CHESTER HIGGINS Jr.

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