What is Whitening
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When to Whiten

What is Teeth Whitening?

Teeth whitening, also known as tooth bleaching, is a common cosmetic dentistry procedure used to brighten the shade of the teeth.  Tooth whitening procedures attempt to remove stains and discoloration to lighten the shade of the teeth.

The Secret: Peroxide Whitening Gel

Teeth whitening works by using a peroxide whitening gel to oxidize or chemically dissolve stains.  The active ingredient for removing stains is hydrogen peroxide which can be found in concentrations ranging from 10% to over 40%.  Carbamide peroxide, which breaks down in the mouth to form hydrogen peroxide is also used, but is roughly only one-third as strong as hydrogen peroxide.  Carbamide peroxide concentrations can be as high as 35%, breaking down to about a 12% hydrogen peroxide concentration.

How Does Whitening Gel Whiten Your Teeth?

To understand how to whiten teeth, you must first understand how teeth get stained in the first place.  Below, we will briefly discuss tooth anatomy and the types of stains that lead to discolored teeth.   

Tooth Anatomy

A tooth is composed of an outer enamel shell, a middle dentin layer, and an inner pulp chamber.  The hard enamel shell insulates and protects the tooth.  The dentin layer which is less brittle than enamel, provides the support and most of the structure of the tooth.  The pulp chamber supplies the nutrients to the tooth and contains the dentin-producing cells. 

Tooth stains fall into two major categories: extrinsic and intrinsic.

Extrinsic (External) Tooth Stains

Extrinsic stains found on the surface of the enamel layer can be removed by a professional cleaning.  Even brushing with an electric toothbrush like a Sonicare or Oral-B can remove some surface staining.  Sometimes, a stain that is not removed will begin to work itself down small pores of the enamel layer.  These persistent stains may still be removed by teeth whitening procedures, though long-lasting stains that have penetrated the dentin layer can be difficult to remove. 

Common Causes of Extrinsic Tooth Stains are:

Eating or drinking intensely-colored foods such as coffee, tea, red wine or orange juice

Smoking

Drugs such as tetracycline mouthrinses

Also affecting the shade of the teeth are the color of the enamel and dentin layers.  Enamel is translucent while dentin is a yellowish color.  A thick layer of enamel would mask the yellow dentin color.  However, a thin enamel layer would show more of the yellowish dentin layer. 

Common Causes for Thinner Enamel are:

Consuming acidic foods and beverages such as cola, lemons, and oranges

Teeth grinding or bruxing

Intrinsic Tooth Stains

Intrinsic stains are found in the dentin and sometimes enamel layers of teeth.  Some intrinsic staining involves exposure to certain chemicals such as fluoride or tetracycline during tooth formation.  Trauma to teeth can also result in intrinsic staining as breakdown of the blood cells in the pulp chamber stain the dentin layer. Intrinsic stains are typically more difficult to treat than extrinsic stains.

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Dr. Yang is a Preferred Invisalign Provider and Board Certified Orthodontist practicing in Redwood City, CA. Read more about Dr. Yang or visit his orthodontic practice online at www.OrthodontistRWC.com.