Advances in the field of cosmetic dentistry are putting smiles on people's faces-literally.

The most sought-after treatment is whitening stained, discolored or dull teeth. Between 1996 and 2000, consumer demand for teeth-whitening grew by more than 300%, according to the American Academy of Cosmetic Dentistry.

The use of porcelain veneers, which can change the look of chipped, cracked or crooked teeth, is also way up. Veneers are ultra-thin, custom-made laminates that are bonded directly to the teeth.

"Improving someone's smile can change their appearance dramatically, making them look healthier, happier and younger," says Manhattan dentist Dr. Jan Linhart, who focuses on cosmetic dentistry.

Linhart has seen a tremendous increase in the number of people coming in for a "smile makeover," as he calls it. Most patients ask for power whitening, which is done in the dentist's office in about an hour and a half.

A gel containing peroxide and other ingredients is placed on the teeth and then power whitening can remove coffee and tobacco stains, and can last a few years.

As for tooth-whitening products sold in stores, they have a lower concentration of peroxide and may help, but only minimally, Linhart says. He also warns that some products advertised on the Internet and elsewhere may cause harm especially if someone has tooth decay or broken fillings and the product seeps into cavities.

The Academy of Cosmetic Dentistry recommends consumers consult with their dentist before trying any cosmetic treatment. Everyone's teeth are different, so an experienced dentist can determine what would work best.

For stains that are resistant to whitening products, Linhart recommends porcelain veneers, which also can repair chipped, cracked or crooked teeth, or to close gaps. Veneers last about 15 years.

Dr. Rock Positano, M.S., M.P.H., D.P.M., is on the faculty and staff of the Weill Medical
College of Cornell University.