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The Hindu
15 April 2009
Washington,USA

New research has shown that human teeth lost some enamel hardness after the application of popular home whiteners.

Researchers noted that teeth can regain their previous hardness after losing small amounts of enamel calcification.

But this is the first study to show at a nano scale, measuring in billionths of a metre, how human teeth are affected by the popular home whiteners.

“There is some significant reduction in nano–hardness of enamel, but we are talking on a very minute scale. So even though it may not be visible to the human eye, it’s important for research because that’s how we improve products,” said Shereen Azer, assistant professor of restorative and prosthetic dentistry at Ohio State University (OSU) and lead author of the study.

Azer and colleagues applied the recommended treatments of five name–brand home whiteners to samples of human teeth and compared the effects to tooth samples that received no treatment.

In all cases, the products reduced the hardness of the enamel as well as what is called the elastic modulus or stiffness, a measure of the ability of the tooth surface to bounce back in response to applied force.

Many studies have sought to determine how tooth whitening affects tooth enamel hardness, but results have been inconclusive, said an OSU release.

Azer said that previous studies measured the loss of enamel hardness in microns, or millionths of a metre, rather than billlionths of a metre used in her study.

The study was published in a recent issue of the Journal of Dentistry.

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