The studies looked at whitening strips, trays filled with gel that are placed over the teeth, and paint-on films. All were available over the counter or by prescription.
While the review authors weren't impressed with the quality of the studies — most were deemed to have a "high" risk of bias — they did find plenty of evidence that the products actually whiten teeth.
"They all work, no matter what type or how they’re applied," Hasson said. However, products with lower concentrations of active ingredients — such as hydrogen peroxide or carbamide peroxide — took longer to work.
In the studies that analyzed side effects, some patients reported mild-to-moderate tooth sensitivity and irritation to the gums. Whitening strips and products with high concentrations of hydrogen peroxide were most likely to cause tooth sensitivity.
The review authors said there's a need for independent studies that compare tooth-whitening products to one another. The authors also called for studies into the effects of using the products for more than six months.
"Most of these products say use them for two weeks and that’s it. But we know that people are using them a lot more than that," said Clifford Whall, a scientist at the American Dental Association who’s familiar with the findings of the review. "I've heard reports of some people using them every Friday night to get ready for the weekend."
Whall said the Cochrane review is "very reasonable," but he cautioned that many products probably weren’t included because only a small number of studies were deemed worthy of review. "We don't know anything about those other products," he said. "We don’t know if they are safe or effective."
The ADA has given its seal of acceptance seal to only two tooth-whitening products other than toothpaste — Colgate Platinum Daytime Professional Whitening System and Opalescence Whitening Gel. Both are available directly from dPage: 1 2 3 Related medicine news :1
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