Teeth whitening is the most popular cosmetic dental treatment due to the fact that it is easy, effective, and affordable. Nowadays, there are a variety of options available to help you whiten your smile by removing years of stains from the surface of your teeth. However, have you ever wondered just how these whitening treatments work?
In the simplest sense, teeth whitening treatments work because of science, more specifically chemistry. But before we get into the science of teeth whitening, we first need to look at the natural color of teeth, as well as what causes teeth to deviate from this natural color. Only then can you understand how teeth whitening procedures work.
For starters, it is important to know that the natural tooth color is not true white. Instead the color of your teeth can vary depending on genetics. There are four basic underlying color tones to teeth including: (A) reddish brown, (B) reddish yellow, (C ) grey, and (D) reddish grey. Within these four groups there are varying shades ranging from light to dark.
As you age, your teeth can darken according to the underlying color tone. Teeth also become yellower in color with age due to the underlying dentin showing through thinning enamel. Staining due to age is an example of intrinsic staining, meaning that it cannot easily be prevented. Intrinsic stains are also harder to remove.
In addition to aging, stains can also form on the surface of your teeth from things like smoking, highly pigmented foods and beverages, and poor oral hygiene. These types of stains are known as extrinsic stains. Since they occur on the surface of your teeth, extrinsic stains are usually easier to eliminate, especially with whitening procedures. They are also more responsive to over the counter whitening treatments and toothpastes.
Both intrinsic and extrinsic stains contain colored molecules that stick to your tooth enamel and get absorbed by the enamel and dentin layers. Over time as more and more of these colored molecules are absorbed, your teeth will appear dull and stained. Therefore teeth whitening procedures work to get rid of stains by eliminating these colored molecules.
Both over the counter and in-office whitening treatments use either hydrogen peroxide or carbamide peroxide. The main difference between the two is the concentration of the ingredient. In-office whitening procedures use a stronger concentration since it is applied by a dentist, while over the counter treatments use a weaker concentration. For this reason, in-office treatments lead to faster and more dramatic results.
During a whitening treatment, the whitening agent is applied to the surface of the teeth. In some cases, a special activating light may also be used. The whitening agent will usually sit in place for 30-60 minutes before being rinsed. As the whitening agent sits on your teeth, it is absorbed into the enamel and dentin layers. The whitening agent molecules then bind with the colored molecules and initiate an oxidation reaction. Without getting too technical, this reaction essentially dissolves colored molecules, which removes stains and returns your teeth to their natural color.
In most cases, people tend to have teeth that are characterized as A3, therefore this is considered to be the natural tooth color. Although A3 is not true white, it appears to be white while still maintaining a natural appearance. True white is B1 and there are also “Hollywood Shades” which are even whiter than that. However, sometimes whiter is not always better, especially since it can make your teeth look unnatural and almost fake. For this reason, most whitening treatments aim to achieve an A3 look.