White sales aren't just for towels and sheets anymore. Ask any dentist.

"Interest in [teeth] whitening has never been higher, especially in the last two years," said Dr. Jorge Perdigao at the University of Minnesota School of Dentistry.

Requests for whitening procedures have increased 300 percent since 1996, according to the American Academy of Cosmetic Dentistry. Whitening has been around more than 20 years, but prices for consumers have remained relatively stable, said Dr. Douglas Lambert of Cosmetic, Family and Sports Dentistry in Edina. Even the methods haven't seen any major technological advances beyond shortened bleaching times.

Those new to bleaching often start with an over-the-counter product for $15 to $50, but for quicker results, they switch to custom-made bleaching trays that range from $250 to $450 at most dental offices. The custom trays usually offer the best bang for the buck.

For more immediate gratification, Zoom and BriteSmile in-office procedures take about 90 minutes. Prices range from $450 to $600. One caveat: The effectiveness of the high-intensity light used to speed the process is questionable. Studies have shown that the light has little or no effect, said Perdigao.

Although the procedures remain the same, consumers can now go to a mall to have their teeth whitened. Last year, six WowSmileXpress locations opened in Twin Cities malls offering do-it-yourself whitening for $99. Customers discuss the treatment with an employee and answer eight questions about dental health. A prefilled mouth guard is filled with carbamide peroxide. The customer inserts the trays and adjusts the LED light while lying in a dentist's chair for 20 minutes.

The Minnesota Board of Dentistry, however, has concerns about mall sites with employees who are neither dentists nor hygienists providing bleaching products without an oral exam, said Marshall Shragg, executive director. The board is also concerned about appropriate infection control procedures at mall stores and is drafting legislation to close the kiosks and storefronts or have them staffed by dental professionals.

Mark Roering, owner of Wow SmileXpress locations, said that the mouth guards are never re-used. The concentrations he uses are higher than most over-the-counter applications, but lower than what dentists use, and the price reflects that. Consumers can pay less using OTC products that require more bleaching time or they can pay more in dentists' offices for quicker results.

But savvy consumers who want quick results don't have to pay top dollar at their dentist. Like nearly every other service or commodity, it pays to shop around.

Dentists who are hungrier for business or starting a practice offer whitening specials in hopes of attracting new patients. Excel Dentistry in St. Louis Park is offering a $99 special on custom whitening trays, normally $275.

"We're offering the deal to attract new patients and a larger business," said Dr. Hatem Alassy. Dr. Shauna Novak of Novak Family Dentistry in Plymouth is offering a 50-percent-off whitening sale through February. Patients get the preliminary exam, custom-made trays and the whitening gel for $150, regularly $300. For $50, her office offers a stronger version of Crest Whitestrips with a more concentrated whitener solution.

At Dau Dental in Minneapolis, Dr. James Dau offers a Zoom whitening special for $350, regularly $500, which includes custom-made bleaching trays for touchups later.

John Ewoldt • 612-673-7633 or jewoldt@startribune.com. If you spot a deal, share it at www.startribune.com/blogs/dealspotter.