Teeth Whitening Products May Be Doing More Harm Than Good

Hydrogen peroxide, the main component of over-the-counter whitening strips, may damage the tooth's second-layer dentin tissue. antoniodiaz/Shutterstock

An active ingredient in whitening strips has been shown to damage the protein-rich tooth layer that connects with the nerves of your teeth.  

Presenting their preliminary findings at this year’s Experimental Biology meeting, researchers found that hydrogen peroxide (H2O2), the main component of over-the-counter whitening strips, may damage the second-layer dentin tissue.

The human tooth is made of three layers: the outer enamel, the dentin layer, and connective tissue that binds the root to the gum. Enamel contains little protein, whereas dentin makes up most of the tooth and has high levels of protein, 95 percent of which is collagen. Preliminary findings from three studies suggest that when whitening strips are applied, hydrogen peroxide used in whitening strips can penetrate the enamel to break down collagen within the dentin layer.

"We sought to further characterize what the hydrogen peroxide was doing to collagen," said lead researcher Kelly Keenan in a statement. "We used entire teeth for the studies and focused on the impact hydrogen peroxide has on the proteins."

In the first study, researchers treated teeth with either one or three rounds of over-the-counter whitening strips that had been processed with artificial saliva and purified with EDTA, a molecule that binds and sticks to calcium. The teeth were left in this treatment for two weeks – a considerably longer time than most people leave whitening strips on – after which researchers measured the number of remaining proteins. When compared against untreated teeth, the whitened teeth showed a loss of protein, suggesting that if hydrogen peroxide can penetrate the enamel, then it can damage non-collagen proteins in the teeth.

The second time around, researchers characterized how H2O2 breaks down various proteins by mixing different concentrations of it with albumin protein, the main protein of human blood plasma, for one hour. When compared with the control, they also found that H2O2 breaks down important proteins even in concentrations similar to those used in whitening strips.

Lastly, researchers treated pure collagen with hydrogen peroxide and analyzed it using a process called gel electrophoresis in order to visualize the protein. Similarly, researchers found that “hydrogen peroxide, even at the concentration used in the whitening strip, can damage the collagen in the dentin provided that the H2O2 can penetrate to the dentin in the teeth,” they wrote.

"Our results showed that treatment with hydrogen peroxide concentrations similar to those found in whitening strips is enough to make the original collagen protein disappear, which is presumably due to the formation of many smaller fragments," said Keenan.

Researchers are quick to caution that their research did not consider whether collagen and other proteins can be regenerated, so it’s unknown if this damage is permanent. Additionally, it is important to note that the "research is just completed and there is not yet a peer-reviewed paper available," according to a conference spokesperson. As such, certain limitations may not have been considered.

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