“A BRIGHT, white smile is vital for making a good first impression” is a typical slogan used by many oral hygiene products. Such emphasis on the importance of having pearly-white teeth has made whitening products from toothpaste to dental floss a “must-have” on people’s beauty lists. However, the chemicals used frequently in teeth whitening products deserve proper examination. The Yonsei Annals consulted Professor Park Jeong-won (Dept. of Conservative Dentistry, Yonsei Univ.) at Gangnam Severance Hospital to unfold the mechanism of teeth whitening.

What causes teeth discoloration?

   Our teeth are one of the most vulnerable parts of our body as they are used and exposed frequently. Primarily divided into four layers—the pulp, dentin, enamel, and cementum—our teeth should be in a hygienic state to remain healthy in the long run[1]. While there has been research on stem cells, regrowth of human teeth has not been completely confirmed[2]. What makes teeth hygiene even more high maintenance is that teeth need to be managed by rectification of daily habits. For instance, teeth tend to discolor heavily by one’s food intake. Repetitive consumption of artificially colored beverages such as energy drinks and coffee, as well as smoking, can stain your teeth. Another primary reason behind the physiological discoloration of our teeth is aging. The pulp—the space between the blood vessels and the nerves of the tissue—narrows as you age and contributes to yellower teeth.

   On the other hand, pathological discoloration due to either direct damage or internal resorption is unlikely to be reversed. Analogous to our body’s response of getting bruises right after we bump hard into other objects, damage in teeth’s blood vessels is also visible to the naked eye. Unlike the soft tissues in other parts of our body, the structural limitation of our teeth makes it almost impossible to supply blood vessels and the tooth is likely to darken after the nerves die from external damage. Meanwhile, aggravation of the nerves can also start from the inner side of the body, accompanying severe aching and drastic change in color. To be specific, internal resorption absorbs the sturdy parts of the tissue; therefore, with a closer look, one will be able to spot light pink on the surface of the teeth which indicates blood vessels showing up. Once they are pathologically damaged and no further action is taken, the color of damaged teeth will either stay the same or get worse, turning either black or dark brown. Dental surgeries such as endodontic treatment that remove either decayed or infected nerves from a pulp have been frequently practiced. The decomposition of damaged pulps after the procedure––if anything––became another cause of discoloration. Dentists often encourage their patients to use preventive measures upon discovering a sense of discoloration, but teeth whitening can be the more effective alternative solution.

How products work to whiten your teeth

   According to Professor Park, ‘whitening’ your teeth is the same as ‘bleaching’ them. Hydrogen peroxide was accidentally discovered to be a decisive chemical for teeth whitening in the 1800s. Upon this revelation, it was widely used for whitening until people found its liquid form inconvenient to apply. Carbamide peroxide found in today’s teeth whitening products can be understood as a gel form of hydrogen peroxide; more specifically, carbamide peroxide chemically breaks down and eventually turns into hydrogen peroxide when it comes in contact with your teeth. Then, these supplied active chemical ingredients in whitening products subsequently cause oxygen to seep into enamel and fine pores, which lightens the color of the teeth by removing the stains whilst the surface is affected as little as possible.

   Later on dentists introduced laser teeth whitening as an innovative method that uses laser or blue colored lights directly on the teeth, drastically shortening the procedure’s duration. The application of whitening gel on the teeth’s surface was quite uncomfortable as patients had to endure dentists poking at the space between their teeth and gums while lying down on a chair for a prolonged period of time[3]. However, the ultra-fine light from the laser heats up the gel, minimizing any possible interaction with dental tools and dissolving the chemicals faster than ever. Professor Park states that laser works more as a catalyst[4] to accelerate chemical reactions to whiten the teeth, and the actual results do not show a striking difference when compared to non-laser teeth whitening[5].

The side effects of teeth whitening

   Although teeth whitening products have become popularized, their improper usage––like over-appliance––could result in irreparable damage to the teeth. Professor Park claims to have seen numerous patients who visited the clinic due to the over-usage of or the accidental consumption of teeth whitening products. The high accessibility of dental products with hydrogen peroxide and carbamide peroxide unintentionally conceals their dangers as chemicals from the ordinary customer. While our body also produces a certain amount of hydrogen peroxide within our cells in order to fight off infection, consuming it in high density is not preferable. Long-term exposure to this chemical leads to inflammation and redness on the inside of our mouths and sometimes the damage in our gums is unlikely to recover.

   Still, Professor Park asserts that teeth whitening does the least harm compared to other dental surgeries that carve out or pull out teeth. However, he warned potential users that any signs of soreness and swelling after the whitening procedure need to be noted. Periodic consultations with the dentist and regular scaling[6] would be ideal, but independently testing out some products that are preferable for your gums and teeth can be an alternative. One or two months of regularly using the product will be enough to evaluate its suitability with your teeth.

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   Frequent use of teeth whitening products can bring you a short-term boost in confidence. However, forming the habit of brushing your teeth regularly and avoiding foods that stain would be a more desirable method of naturally sustaining your oral health.

[1] Scientific American

[2] Healthline

[3] Dental Innovations

[4] Catalyst: An object or a chemical that helps expedite a chemical reaction

[5] Healthline

[6] Scaling: A dental procedure that uses a tool called a “scaler” to remove plaque from teeth