Are whitening toothpastes a bright idea?

Whitening mania is especially obvious in the toothpaste aisle. Just about every major brand now comes in special whitening formulas.

While strips and trays work by soaking the teeth in bleach for long stretches of time, whitening toothpastes take a faster approach. They generally rely on abrasives (toothpaste companies prefer to call them "polishers") that help remove surface stains left behind by coffee, cigarettes, juices and foods.

Crest, a Procter & Gamble brand, offers 3D White Vivid and 3D White Advanced Vivid. Both varieties contain hydrated silica as an abrasive. The advanced version, which comes out of the tube in two separate chambers, also has sodium hexametaphosphate, a compound that helps loosen the stains so the abrasives can do their job. Users are instructed to brush after meals or at least twice a day. Expect to pay about $4 for the 4.1-ounce tube of either product.

Rembrandt, a Johnson & Johnson company, has built its brand around the promise of whitening. Both its Intense Stain and Deeply White toothpastes contain hydrated silica. Deeply White also has the bleaching agent urea peroxide. Users are instructed to brush twice daily "and after meals if possible." A 3-ounce tube of Intense Stain costs about $8, and a 2.6-ounce tube of Deeply White goes for about $7.

The claims

The label for Crest 3D White Vivid claims it can remove 80% of surface stains in two weeks, and the advanced version says it removes 90% of surface stains in the same period of time. Alissa Fitzgibbons, a spokeswoman for Procter & Gamble, says "a lot of consumers see great results" from the toothpastes. She adds that people who want extra whitening often try Crest WhiteStrips or other bleaching products.

The Rembrandt website says the peroxide in the Deeply White toothpaste targets "deep stains" in the teeth and that Intense Stain is "expertly formulated to remove tough stains, prevent new stains from sticking and actively restore and strengthen tooth enamel." Teresa Panas, a spokeswoman for Johnson & Johnson, says that Deeply White "polishes away surface stains and safely whitens below the enamel." She also says that Intense Stain contains "micro-polishers" that go to work on stains "like red wine, soda, coffee and tobacco."

The bottom line

There's no doubt that whitening toothpastes can clean stains off teeth and give them a little extra gleam. But the term "whitening" is misleading, says Dr. Vincent Mayher, a Haddonfield, N.J., dentist and the past president of the Academy of General Dentistry. Unlike trays and strips that can bleach deep within a tooth, he explains, toothpastes can reach only the surface. Besides, he adds, bleaches in toothpastes are useless because they'll get rinsed away before they do anything.

Still, getting rid of surface stains can really brighten a smile, and Mayher says whitening toothpastes can be worth a try as long as a user doesn't expect miracles. If a person has his or her teeth bleached, whitening toothpastes can help keep the teeth from turning yellow again, he adds.

But Mayher also warns of potential problems. Over time, he says, an abrasive toothpaste could wear away the outer layer of enamel on a tooth, exposing the yellowish dentin beneath. "You could actually end up making your teeth look less white." Plus, the abrasives in whitening toothpastes can be painful for some people, so those with sensitive teeth should be careful, he adds.

In a study published this year in the Journal of Clinical Dentistry, investigators at Thermetric Technologies Inc., a dental research firm in Noblesville, Ind., and the Health Science Research Center at Indiana University-Purdue University in Fort Wayne tested the abrasiveness and cleaning power of 26 whitening toothpastes on enamel from cow teeth. Crest White Vivid ranked 17th in terms of cleaning but was the fourth-most abrasive. Anything with an RDA (relative dentin abrasion) score above 100 is generally considered highly abrasive, and anything above 150 is considered potentially damaging to enamel. Crest White Vivid scored above 200.

Rembrandt Intense Stain was only mildly abrasive (RDA about 90), but it was also in the middle of the pack in terms of cleaning power. The toothpaste with the top marks for stain removal — Ultrabrite Advanced Whitening from Colgate — was also one of the most abrasive, reaching an RDA of about 260. The study didn't include either Crest 3D White Advanced Vivid or Rembrandt's Deeply White.

In general, the most effective whitening toothpastes are also the most abrasive, says Bruce Schemehorn, the lead author of the study. To his mind, the ideal whitening toothpaste would be both gentle on the enamel and tough on stains. "I've been studying this for 30 years, and I haven't found it yet," he says.