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.

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.

Teeth Whitening Options

Three major teeth whitening options are available today. All three rely on varying concentrations of peroxide and varying application times.

In-Office Whitening

Significant color change in a short period of time is the major benefit of in-office whitening. This protocol involves the carefully controlled use of a relatively high-concentration peroxide gel, applied to the teeth by the dentist or trained technician after the gums have been protected with a paint-on rubber dam. Generally, the peroxide remains on the teeth for several 15 to 20 minute intervals that add up to an hour (at most). Those with particularly stubborn staining may be advised to return for one or more additional bleaching sessions, or may be asked to continue with a home-use whitening system.

Professionally Dispensed Take-Home Whitening Kits

Many dentists are of the opinion that professionally dispensed take-home whitening kits can produce the best results over the long haul. Take-home kits incorporate an easy-to-use lower-concentration peroxide gel that remains on the teeth for an hour or longer (sometimes overnight). The lower the peroxide percentage, the longer it may safely remain on the teeth. The gel is applied to the teeth using custom-made bleaching trays that resemble mouth guards.

Hydrogen Peroxide vs. Carbamide Peroxide

The bleach preference for in-office whitening, where time is limited, is powerful and fast-acting hydrogen peroxide. When used in teeth bleaching, hydrogen peroxide concentrations range from approximately nine percent to 40 percent.

By contrast, the bleach of preference for at-home teeth whitening is slower acting carbamide peroxide, which breaks down into hydrogen peroxide. Carbamide peroxide has about a third of the strength of hydrogen peroxide. This means that a 15 percent solution of carbamide peroxide is the rough equivalent of a five percent solution of hydrogen peroxide.

How White Can You Go? A Matter of Esthetics

Teeth whitening results are subjective, varying considerably from person to person. Many are immediately delighted with their outcome, while others may be disappointed. Before you embark on any whitening treatment, ask your dentist for a realistic idea of the results you are likely to achieve and how long it should take to achieve them. Expectations play a major role in teeth whitening.

Whitening Shade Guides

In the dental office, before-and-after tooth color is typically measured with shade guides. These are hand-held displays of wide ranges of tooth colors. (Dentists also use them in choosing crown and other restoration shades.)

The standard-setter among them has long been the Vitapan Classic Shade Guide. This shade guide standard incorporates 16 shades, systematically arranged from light to dark into four color groups, and provides a universal tooth-color terminology.

While whitening can occasionally lighten tooth color by nine or more shades, most of those who bleach their teeth are likely to see a change of two to seven shades.

Does it hurt? What are the side effects of teeth whitening?

Teeth whitening treatments are considered to be safe when procedures are followed as directed. However

• Sensitivity: In very few cases Bleaching can cause a temporary increase in sensitivity to temperature, pressure and touch. This is likeliest to occur during in-office whitening,
  
  Whitening sensitivity lasts no longer than a day or two, Desentesizing toothpaste can be prescribed if needed.
• Pregnant  women are advised to avoid teeth whitening.
• Technicolor teeth: Restorations such as bonding, dental crowns or porcelain veneers are not affected by bleach and therefore maintain their default color while the surrounding teeth are whitened. This results in what is frequently called “technicolor teeth.”

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.