Dentists all over the United States are having a hard time keeping up with the demand for brighter, white teeth. And because these services can be expensive, many turn to whitening strips that they can apply themselves at home. However, Americans' obsession with perfect white teeth might sometimes backfire if these strips aren't used accordingly.
According to a study performed by researchers at Stockton University in Galloway, NJ, whitening strips can damage the protein-rich dentin tissue found beneath the tooth’s protective enamel.
Teeth are made up of three distinct layers. The innermost layer is a connective tissue that helps keep the teeth safely in place; the middle layer is made of dentin, the yellowish tissue that makes up the bulk of all teeth; and the external layer is made of enamel, which determines the brightness of teeth.
Teeth-whitening strips are made of a flexible plastic that is coated in a thin layer of whitening gel. The main active ingredient is hydrogen peroxide, an oxidizing agent that is also the main substance found in products that bleach hair.
Overusing hydrogen peroxide as a color-lightening agent is known to damage the hair and the scalp. And, according to researchers led by Kelly Keenan, Associate Professor of Chemistry at Stockton, hydrogen peroxide can have a similar effect on teeth, potentially attacking the dentin layer of teeth.
The Stockton professor and her students reported that perhydroxyl radicals produced by peroxide break up long-chain organic molecules into smaller molecules.
Whitening strips are applied to the teeth such that the gel penetrates the tooth and starts the whitening process. Even the best teeth whitening kits have to be applied each day for two to three weeks.
The researchers followed these instructions in the lab using human teeth extracted from cadavers. In order to model the human mouth environment, the teeth were soaked in artificial saliva and washed.
Then, the research team measured the level of collagen and other proteins that make up dentin and compared the results to unbleached teeth, as well as a different set of teeth that underwent whitening three times.
The results suggest that hydrogen peroxide can pierce the enamel layer and infiltrate dentin, which is made of 90-95% collagen. In the case of teeth that were whitened three or more times, the collagen seemed close to disappearing.
“We sought to further characterize what the hydrogen peroxide was doing to collagen,” said Keenan. “We used entire teeth for the studies and focused on the impact hydrogen peroxide has on the proteins.”
In another experiment, the researchers treated pure collagen with hydrogen peroxide and then analyzed the protein using a gel electrophoresis laboratory technique that allows 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.
Does this mean that using whitening strips can damage your teeth? The research suggests that this may be a risk when using such products, although more research is required as the study itself has some important limitations. For instance, it didn't consider the fact that collagen can be regenerated. Also, the effect of the strips wasn't studied in a real human mouth, which might prove to be very important.
But, as the teeth whitening industry is set to grow to $7.4 billion by 2024, cosmetic dentists are becoming increasingly concerned as to what this may mean for patients.
If you'd like to have whiter, brighter teeth without having to risk your oral health, dental experts recommend avoiding foods that are known to cause staining such as coffee, tea, red wine, and soda. If you consume these foods, rinse your mouth with water right after drinking or eating in order to reduce the staining effect.