Dental hygienist Trish Wintch calls herself a walking advertisement for teeth bleaching. Ten years ago, a dentist made her a plastic tray. She filled it with gooey chemicals, wore it night and day for a month.

Trish Wintch: ) "I had really dark teeth and I wanted them lighter."

Dr. Steven Smith, dentist: "I've had patients literally cry. Tears come to their eyes when they see the color of their teeth as they progressed."

Dentist Steven Smith smiles when he talks about teeth bleaching.

Business is booming. Here and just about everywhere that offers the service, which almost always consists of a dentist-supervised take home chemical kit.

Made to order pearly whites in just two weeks.

Professional bleaching takes a bite out of your wallet-- between $200 and $500. Some do-it-yourself kits cost only $50. But the American Dental Association warns that such kits may eat away at your teeth and gums.

When it comes to whitening toothpastes, read the label, there's usually nothing more inside than fluoride, same as regular toothpaste. But these identical toothpastes do not have identical price tags.

Dr. Steven Smith, dentist: "Toothpastes have very little effect on tooth long term. That's basically a surface stain remover, period."

Dr. Smith says bleaching works better and lasts longer than dentists ever thought. But patients should be realistic about their expectations.

Dr. Steven Smith, dentist: "Some people think that by getting white teeth they're going to have a beautiful white mouth. They kind of have it in their mind an idea that they're going to have a Hollywood smile, and they bleach. So, that will never happen."

A comparison study of all tooth bleaching techniques shows laser bleaching is no better than the chemicals.