(Image source from: MarketWatch)

Teeth-whitening products are widely used to guarantee a bright smile, but what one should know before gobbling the products is they are indeed capable of harming protein-rich tooth layers.

Researchers, in three new studies, found that hydrogen peroxide, the active component in the over-the-counter whitening strips, can be able to harm the protein-rich dentin tissue found beneath the tooth's protective enamel.

The tooth is made of three layers: Enamel - the outermost layer of the tooth. Enamel is the hardest, most mineralized tissue in the body yet it can be damaged by decay if teeth are not cared for properly. Dentin - the layer of the tooth under the enamel, and the connective tissue that binds the roots to the gum.

Almost all the studies of whitening strips have focused on tooth enamel, which comprises very little protein.

Kennan's research team focuses on dentin, which makes up most of the tooth and has high levels of protein, most of which is collagen. It is well established that hydrogen peroxide can get into the enamel and dentin. Former work by the researchers showed that collagen in the dentin layer decreased when teeth were treated with whitening strips.

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

As part of the study, the researchers demonstrated that the major protein in the dentin is converted to smaller fragments when treated with hydrogen peroxide. In additional experiments, they treated pure collagen with hydrogen peroxide and then analyzed the protein using a gel electrophoresis laboratory technique that lets the protein to be visualized.

"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.

By Sowmya Sangam