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Using digital imaging to measure color changes in the teeth before and after the treatments, researchers found those who used the strips experienced a 91% improvement in yellowness reduction compared with those who used the trays containing 16% carbamide peroxide.
Researchers also found that use of the strips over 21 days produced much less tooth sensitivity and gum irritation than use of the trays with 20% peroxide gel for 14 nights.
Similar tooth-whitening strips and tray systems are available over the counter, but they contain lower concentrations of peroxide than the ones used in the studies. That means it will take longer to produce results, and the whitening effects may not be as dramatic.
Although tooth-whitening strips may be less expensive that custom-made tray systems, Mike Malone, DDS, president of the American Academy of Cosmetic Dentistry, says there's also another important consideration that was not addressed by these studies.
"The biggest difference between strip bleaching and tray bleaching is the number of teeth affected," says Malone. "Strips that are presently available are only long enough to cover 6-8 teeth."
"Someone with a fairly wide smile will find that their front teeth are white, but the other teeth that show on the sides will not be affected," Malone tells WebMD.
Malone says at-home teeth whitening is not recommended for people with porcelain crowns, bonding, or other tooth restorations. Peroxide-based bleaches will only bleach natural teeth and will not whiten caps, crowns, veneers, or filings.
In addition, people that need whitening of discolored teeth -- such as teeth stained gray from the use of tetracycline -- won't experience good results with home teeth whiteners.
Malone says he expects to continue to see improvements in tooth whitening technologies available at the dentist's office and for home use.
"I think we are going to see the materials work a little faster and probably become a little more comfortable," says Malone.
SOURCES: Annual meeting of the International Association of Dental Research, Honolulu, March 10-13, 2004. Ingvar Magnusson, DDS, PhD, professor of oral biology, University of Florida. Michael Malone, DDS, president, American Academy of Cosmetic Dentistry. News release, University of Florida.