April 15, 2009

Home tooth bleaches reduce enamel strength

U.S. researchers say teeth lose some enamel hardness after using in-home teeth bleaching.

The study, published in the Journal of Dentistry, was able to show on a nanometer scale -- one measuring in billionths of a meter -- how home tooth bleaching products affect tooth enamel.

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, study lead author Shereen Azer of Ohio State University in Columbus said in a statement.

Azer and colleagues applied five name-brand home whiteners to samples of human teeth and compared the effects to tooth samples receiving no treatment. In all cases, the products reduced the hardness of the enamel as well as stiffness -- a measure of the ability of the tooth surface to bounce back in response to applied force.

The average loss of enamel ranged from 1.2-2 nanometers on the treated teeth. The control teeth, on average, gained 0.4 nanometers of hardness over the treatment time frame. The stiffness of treated teeth was reduced by an average of between 6 percent and 18.8 percent -- depending on the type of treatment.