Teeth lost some enamel hardness after the application of several different at-home teeth-whitening products, according to a recent Ohio State University (OSU) study (Journal of Dentistry, March 2009, Vol. 37:3, pp. 185-190).
The researchers also noted a reduction in elastic modulus or stiffness, a measure of the ability of the tooth surface to bounce back in response to applied force.
The study is the first to show how human teeth are affected by the popular home whiteners at nanometer scale, according to the researchers.
"There is some significant reduction in nanohardness 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, B.D.S., an assistant professor of restorative and prosthetic dentistry at OSU and lead author of the study, in a press release.
Dr. Azer and his team used five name-brand home whiteners on samples of human teeth and compared the effects to tooth samples that received no treatment. The products used in the study were Crest Whitestrips Premium Plus, Crest Whitestrips Supreme, Nite White ACP, Oral B Rembrandt, and Treswhite Opalescence.
"Nanohardness and elastic modulus of human enamel were significantly decreased after the application of home-bleaching systems," the authors concluded.
Previous studies have measured the loss of enamel hardness in microns rather than on the nanometer scale used in his study, according to Dr. Azer. "So this just gives us a better understanding of precisely how these products affect human teeth," he said.
For more details on the study, click here.
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