Teeth Whitening: The Science Behind a Beautiful Smile

Many people yearn for a beautiful smile that brightens their entire face. After all, our face is the first thing people see when they look at us and a great smile is definitely something worth remembering. Unfortunately, not everyone is born with a perfect smile. In fact, most people undergo some type of dental or orthodontic treatment in order to enhance their smile. 

While modern dentistry has a variety of cosmetic dental treatments to improve the aesthetics of your smile, there is no easier treatment that teeth whitening. In as little as a single office visit, teeth whitening can instantly whiten your teeth by several shades to make them appear whiter and brighter. Just this slight change in shade can improve the aesthetics of your smile and even make your entire face appear younger. 

To many, this may seem too good to be true. I mean, how exactly does a single, minimally-invasive dental appointment leave you with a brighter smile? Are teeth whitening procedures really that simple? The answer is yes, teeth whitening procedures really are that simple and the results are almost immediately apparent. However the science that backs up teeth whitening is not quite as simple as the procedure itself. Let’s take a look at just how teeth whitening works. 

To understand how teeth whitening works, we first need to have a brief understanding about tooth anatomy. The human tooth is composed of three different layers: the enamel, dentin, and pulp layer. The enamel layer is the outermost and hardest layer of your tooth. In fact, the enamel is the layer that you see when you smile and that you brush everyday. 

Model of a tooth showing its three layers

Below the enamel layer, lies the dentin layer. This layer is not nearly as hard as the enamel and is actually somewhat porous, meaning that it has passageways that lead to the dental pulp. Finally, the innermost layer of your tooth is the dental pulp, which contains blood vessels and nerves. 

When your teeth become stained, it is the enamel, dentin, or sometimes both that become stained. While enamel is always visible, as it wears down the dentin may become visible as well. In some cases, teeth can appear stained because the enamel is thin and the dentin layer, which is naturally yellow, is showing through. 

Depending on the layer that has been stained, there are two different types of stains that can occur on teeth. Namely, these are extrinsic and intrinsic stains. Extrinsic stains are those that affect the enamel layer. Generally speaking, extrinsic stains are caused by external factors such as smoking, consuming highly pigmented foods or beverages, or poor oral hygiene. However, they can also occur as the result of taking certain antibiotics or from the metals in amalgam fillings or other metal restorations. 

Sugar, soda, and a slice of cake attacking a giant model tooth

Intrinsic stains, on the other hand, are those that affect the dentin layer. Intrinsic stains are most commonly caused by uncontrollable factors such as genetics, age, and developmental disorders prior to tooth eruption. However, they can also be the result of taking certain antibiotics or of excess fluoride. 

Now here’s where it gets a bit tricky. All stains are made up of colorless compounds with the biological potential to become pigmented called chromogens. In particular, the chromogens associated with teeth stains are pigment-producing, meaning that they result in showing some kind of color. The more of these chromogens that accumulate, the greater the pigment of the stain. Chromogens can also be made up of large organic compounds or metal containing compounds, depending on the type of stain. 

Teeth stains can come in a variety of colors, and your dentist can learn a lot about your habits just by observing what color stain you have. For example: 

  • Smoking usually causes dark tar stains and yellowish nicotine stains. 
  • Drinking coffee, tea, or dark colas generally causes brownish-yellow stains. 
  • Antibiotics, such as tetracycline or doxycycline, can cause dark yellow-brown or blue-green stains to appear in horizontal striped patterns
  • Metals from restorations can cause green, blue or grayish-black stains
  • Age generally causes yellowish stains when the enamel thins and the dentin shows through
  • Excess fluoride can cause chalky white or brown spots, patches, or lines

Teeth whitening works against these stains by a chemical process called oxidation. Oxidation is half of what chemists call a redox reaction. In a redox reaction, one chemical is oxidized, or loses electrons, and another chemical is reduced, or gains an electron. Without getting too complicated, rust formation and the burning of fuel are examples of two everyday redox reactions that occur at different rates.

In the case of teeth whitening, hydrogen or carbamide peroxide are the active ingredients in the whitening agent. They are highly similar in chemical composition, as carbamide peroxide breaks down into hydrogen peroxide when applied to the teeth. During a teeth whitening procedure, it is the hydrogen peroxide that becomes oxidized and breaks the double chemical bonds of the chromogens, scattering their molecules. Because stains result from accumulations of chromogens, once scattered they appear lighter in color. 

However, it is also important to note that teeth whitening itself does not always guarantee perfectly white teeth. This is because the effects of teeth whitening are also based upon your natural tooth color. While many people believe that white is the natural color of teeth, this is not the case. In fact, all teeth actually have an underlying color tone that is determined by genetics. 

There are four basic color tones that your teeth can be: (A) reddish brown, (B) reddish yellow, (C ) gray, and (D) reddish gray. When preparing for a whitening treatment, your dentist will use a shade guide with one of four different shades to determine your natural tooth color and show your anticipated results. Depending on whether you are an A, B, C, or D, you can expect to have different results. 

Shade guide showing the four color tones of teeth

Although most people say they want “white” teeth, true white may not actually be the best look for your smile. In actuality, the average tooth color is A3, which is not true white and has a slight red-yellow tint. However, even with this slightly colored tint, many people find the color of A3 to be aesthetically pleasing and would rate those with A3 teeth as having a beautiful smile. Now true white, on the other hand, is B1, which is the whitest natural shade. 

With teeth whitening procedures, you don’t have to completely whiten your teeth to “true white” levels to see results. In fact, most people do not whiten all the way to B1 because they wish to have a natural appearance, and teeth that appear too white may not have the most natural look. Still, whitening your teeth can remove years of stains and discolorations, making your smile appear both younger and brighter. And now that you understand the science behind teeth whitening, you don’t have to doubt that an hour in the dentist’s chair is definitely worth the results. 

To learn more about your teeth whitening options or to make an appointment, call our office to schedule a consultation with Palm Beach’s Top Dentists, Drs. Lerner and Lemongello. 

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