In the blossoming world of cosmetic dentistry, teeth whitening reigns supreme. Universally valued by men and women alike, whitening (or bleaching) treatments are available to satisfy every budget, time frame and temperament.

Whether in the form of one-hour bleaching sessions at your dentist's office, or home-use bleaching kits purchased at your local drugstore, teeth whitening solutions abound. Yet only 15 percent of the population has tried the cosmetic procedure, and misinformation on the subject is rife.

The long and the short of it is that teeth whitening works. Virtually everyone who opts for this cosmetic treatment will see moderate to substantial improvement in the brightness and whiteness of their smile. However, teeth whitening is not a permanent solution and requires maintenance or “touch-ups” for a prolonged effect.

Bleaching vs. Whitening

According to the FDA, the term “bleaching” is permitted to be used only when the teeth can be whitened beyond their natural color. This applies strictly to products that contain bleach – typically hydrogen peroxide or carbamide peroxide.

The term “whitening,” on the other hand, refers to restoring a tooth's surface color by removing dirt and debris. So any product that cleans (like a toothpaste) is considered a whitener. Of course, the term whitening sounds better than bleaching, so it is more frequently used – even when describing products that contain bleach.

Why Teeth Whitening? Examining Enamel

Most of us start out with sparkling white teeth, thanks to their porcelain-like enamel surface. Composed of microscopic crystalline rods, tooth enamel is designed to protect the teeth from the effects of chewing, gnashing, trauma and acid attacks caused by sugar. But over the years enamel is worn down, becoming more transparent and permitting the yellow color of dentin – the tooth's core material – to show through.

During routine chewing, dentin remains intact while millions of micro-cracks occur in the enamel. It is these cracks, as well as the spaces between the crystalline enamel rods, that gradually fill up with stains and debris. As a result, the teeth eventually develop a dull, lackluster appearance.

Teeth whitening removes the stains and debris, leaving the enamel cracks open and exposed. Some of the cracks are quickly re-mineralized by saliva, while others are filled up again with organic debris.

Tooth Discoloration: The Two Types of Tooth Stains

There are two categories of staining as it relates to the teeth: extrinsic staining and intrinsic staining.

Extrinsic stains are those that appear on the surface of the teeth as a result of exposure to dark-colored beverages, foods and tobacco, and routine wear and tear. Superficial extrinsic stains are minor and can be removed with brushing and prophylactic dental cleaning. Stubborn extrinsic stains can be removed with more involved efforts, like teeth bleaching. Persistent extrinsic stains can penetrate into the dentin and become ingrained if they are not dealt with early.

Intrinsic stains are those that form on the interior of teeth. Intrinsic stains result from trauma, aging, exposure to minerals (like tetracycline) during tooth formation and/or excessive ingestion of fluoride. In the past, it was thought that intrinsic stains were too resistant to be corrected by bleaching. Today, cosmetic dentistry experts believe that even deep-set intrinsic stains can be removed with supervised take-home teeth whitening that is maintained over a matter of months or even a year.

What Causes Tooth Staining?

Age: There is a direct correlation between tooth color and age. Over the years, teeth darken as a result of wear and tear and stain accumulation. Teenagers will likely experience immediate, dramatic results from whitening. In the twenties, as the teeth begin to show a yellow cast, teeth-whitening may require a little more effort. By the forties, the yellow gives way to brown and more maintenance may be called for. By the fifties, the teeth have absorbed a host of stubborn stains which can prove difficult (but not impossible) to remove.

Starting color: We are all equipped with an inborn tooth color that ranges from yellow-brownish to greenish-grey, and intensifies over time. Yellow-brown is generally more responsive to bleaching than green-grey.

Translucency and thinness: These are also genetic traits that become more pronounced with age. While all teeth show some translucency, those that are opaque and thick have an advantage: they appear lighter in color, show more sparkle and are responsive to bleaching. Teeth that are thinner and more transparent – most notably the front teeth – have less of the pigment that is necessary for bleaching. According to cosmetic dentists, transparency is the only condition that cannot be corrected by any form of teeth whitening.

Eating habits: The habitual consumption of red wine, coffee, tea, cola, carrots, oranges and other deeply-colored beverages and foods causes considerable staining over the years. In addition, acidic foods such as citrus fruits and vinegar contribute to enamel erosion. As a result, the surface becomes more transparent and more of the yellow-colored dentin shows through.

Smoking habits: Nicotine leaves brownish deposits which slowly soak into the tooth structure and cause intrinsic discoloration.

Drugs / chemicals: Tetracycline usage during tooth formation produces dark grey or brown ribbon stains which are very difficult to remove. Excessive consumption of fluoride causes fluorosis and associated areas of white mottling.

Grinding: Most frequently caused by stress, teeth grinding (gnashing, bruxing, etc.) can add to micro-cracking in the teeth and can cause the biting edges to darken.

Trauma: Falls and other injuries can produce sizable cracks in the teeth, which collect large amounts of stains and debris.

Maintaining Your Whiter Smile

To extend the longevity of newly whitened teeth, dentists are likely to recommend:

  • At-home follow-up or maintenance whitening – implemented immediately or performed as infrequently as once a year.
  • Avoiding dark-colored foods and beverages for at least a week after whitening.
  • Whenever possible, sipping dark-colored beverages with a straw.
  • Practicing excellent oral hygiene – brushing and flossing after meals and at bedtime.

Caveats

In addition to the aforementioned risk factors, a number of caveats should be considered before undergoing teeth whitening:

  • No amount of bleaching will yield “unnaturally” white teeth.
  • Whitening results are not fully seen until approximately two weeks after bleaching. This is an important consideration if you are about to have ceramic restorations and want to be sure the color matches that of your newly bleached teeth.
  • If cosmetic bonding, porcelain veneers or other restorations are part of your treatment plan, they should not be placed until a minimum of two weeks following bleaching to ensure proper adhesive bonding, function and shade matching.
  • To avoid the technicolor effect, tooth-colored restorations will likely need replacement after bleaching.
  • Recessed gums often reveal their yellowish root surfaces at the gum line. That yellow color has proven difficult to bleach.
  • Pregnant or nursing women are advised to avoid teeth whitening. The potential impact of swallowed bleach on the fetus or baby is not yet known.