Teeth Whitening: How it Works

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.

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.

Over-the-Counter Whitening

The cheapest and most convenient of the teeth whitening options, over-the-counter bleaching involves the use of a store-bought whitening kit, featuring a bleaching gel with a concentration lower than that of the professionally dispensed take-home whiteners. The gel is applied to the teeth via one-size-fits-all trays, whitening strips or paint-on applicators. In many cases this may only whiten a few of the front teeth unlike custom trays that can whiten the entire smile.

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.

Teeth Whitening Risks

Teeth whitening treatments are considered to be safe when procedures are followed as directed. However, there are certain risks associated with bleaching that you should be aware of:

• Sensitivity: Bleaching can cause a temporary increase in sensitivity to temperature, pressure and touch. This is likeliest to occur during in-office whitening, where higher-concentration bleach is used. Some individuals experience spontaneous shooting pains (“zingers”) down the middle of their front teeth.
  
  Individuals at greatest risk for whitening sensitivity are those with gum recession, significant cracks in their teeth or leakage resulting from faulty restorations. It has also been reported that redheads, including those with no other risk factors, are at particular risk for tooth sensitivity and zingers.
  
  Whitening sensitivity lasts no longer than a day or two, but in some cases may persist up to a month. Some dentists recommend a toothpaste containing potassium nitrate for sensitive teeth.
• Gum irritation: Over half of those who use peroxide whiteners experience some degree of gum irritation resulting from the bleach concentration or from contact with the whitening trays. Such irritation typically lasts up to several days, dissipating after bleaching has stopped or the peroxide concentration lowered.
• 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.

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.

In-Office Teeth Whitening: Professional Advantages, Costs and Options

Professional in-office teeth whitening is the most popular cosmetic dental procedure in the world today. Unlike home-use whitening systems that incorporate low-dose bleaching agents, in-office whitening (also known as power bleaching, power whitening, professional whitening or chairside whitening) takes place under carefully monitored conditions which allow for the safe, controlled, pain-free use of a relatively high concentration of bleaching gel – yielding results that are visible immediately.

Advantages of In-Office Whitening

• No other teeth whitening procedure produces faster results.
• This is the safest form of tooth bleaching.
• Gum and tooth sensitivity (formerly drawbacks to in-office bleaching) are more controllable today due to thicker peroxide gels (that don't soak into the teeth as much as previous gels) and the use of desensitizers such as potassium nitrate and fluoride.

Disadvantages of In-Office Whitening

• In-office bleaching is more expensive than take-home alternatives. Its cost, on average, is $650, compared to $400 for take-home trays and under $100 for over-the-counter bleaching trays or whitening strips.
• Results can be unpredictable, depending on factors such as age, heredity and the type of staining that is present.
• In-office bleaching is not a permanent solution. Shortly after treatment is completed, the teeth resume accumulating stains. Many dentists therefore recommend home maintenance follow-up with a lower-percentage bleach that can be kept on the teeth for longer periods of time.

Stains That are Best Removed with In-Office Whitening

Chairside whitening removes organic stains or discolorations primarily caused by:

• Aging. Over time, the teeth darken with a yellow, brown, green or grey cast (which may be due to heredity and/or eating habits). Yellowed teeth tend to whiten most readily.
• Consumption of certain foods (notably coffee, red wine, sodas and dark-colored vegetables and fruits).
• Tobacco use.

Stains Resistant to In-Office Whitening

• Teeth with certain stains – typically those that are inorganic – do not respond well to in-office whitening. In fact, these teeth may look even darker after the surrounding teeth have been whitened.
• Trauma, which causes the dentin to darken.
• Tetracycline antibiotics ingested during tooth-formation. These drugs chemically bind with the crystalline structure of both the tooth's enamel and underlying dentin.
• Overexposure to fluoride, which can cause fluorosis, resulting in tooth discoloration.

Are you a Candidate for In-Office Whitening?

This procedure is not suitable for those with the following conditions:

• Tooth and gum hypersensitivity. To avoid a hypersensitive reaction, your dentist is likely to recommend take-home bleaching trays with a low concentration of carbamide peroxide – which is not as potent as hydrogen peroxide.
• Deep and intractable staining. Some stains are resistant to high-concentration in-office bleaches. In such cases, dentists may recommend a supervised regimen of intensive take-home bleaching or alternatives to peroxide bleaching such as bonding, crowns or porcelain veneers.
• Teeth that have become transparent with age. This is particularly true of the front teeth, which are thin to begin with.

Prepping the Teeth

• Your teeth will likely be given a prophylactic cleaning to clear away plaque and debris that have collected on the surface and between the teeth.
• A dental exam will be performed (often in tandem with the prophylactic cleaning) to check for potential problems such as severe tooth decay, cracks and gum disease. Bleaches can cause varying degrees of irritation if these conditions are present. Your dentist will likely delay the whitening procedure until such problems have been corrected.
• Photos may be taken of your teeth, and their color measured on a shade guide. This provides a benchmark for assessing your whitening progress.

The In-Office Teeth Whitening Procedure

While details may vary, a fairly standard routine is followed. Typically, the steps involved are not painful or uncomfortable; in fact, many patients doze or watch a DVD or TV during the procedure.

• A cheek retractor is inserted into the mouth, exposing all the “esthetic zone” teeth (teeth that are visible when you smile).
• A liquid rubber dam or hardening resin is painted onto the gum tissue to protect against any irritation caused by the bleaching gel.
• A bleaching gel containing hydrogen peroxide is applied to the esthetic zone teeth and kept on for approximately 15 to 30 minutes.
• The bleaching gel is suctioned or washed off, and fresh gel is applied for one or more additional periods of 15 to 30 minutes.
• Some whitening treatments incorporate an intense light that is focused on the teeth and is said to activate or enhance the bleaching process. Opinions vary as to whether this light improves the bleaching outcome.
• Between gel applications, the teeth are checked to see how well they have whitened, and whether more bleach needs to be applied.
• After the final gel application, the cheek retractors are removed, the patient rinses and the immediate post-treatment shade change is measured. The teeth may whiten by as few as two to three shades or as many as eight (out of a total of 16). Part of the whitening effect is due to dehydration during the bleaching process, which makes the teeth look whiter than their true new color. That color will emerge after a couple of days.

If a satisfactory level of whitening hasn't been achieved, your dentist may recommend follow-up in-office bleaching at a future date, and/or a regimen of take-home bleaching trays.

In-Office Teeth Whitening Options

A number of brand-name whitening systems are in use at dental offices today. Here is a rundown of those most readily available:

BriteSmile

Known for its gentleness and ease of access, the BriteSmile bleaching system is available at participating dental practices and self-standing BriteSmile whitening locations throughout the country.

The BriteSmile whitening procedure features proprietary hydrogen peroxide whitening gels (concentrations of 15 percent and 25 percent), which are pH balanced to maximize whitening efficacy, and which contain glycerin and water to help minimize tooth dehydration. Dental practices offer both gels, while BriteSmile facilities feature only the 15 percent gel. Generally, the gels are applied to the teeth for three 20-minute intervals.

During each application, the teeth are illuminated with a blue lighting system that is shaped to reach all esthetic zone teeth at the same time.

Total chair time: Approximately one hour.

Opalescence Boost

Praised for the viscosity of its bleaching gel – a sticky quality that is considered a major plus in tooth-bleaching – Opalescence Boost relies on chemistry for achieving its effects, and does not include the use of a special light activator. Its 38 percent solution of hydrogen peroxide gel contains a unique patented component called PF, a mix of potassium nitrate (reducing the risk of sensitivity associated with tooth whitening) and fluoride (the enamel-strengthener which reduces the risk of cavities).

Total chair time: One to two hours.

Sapphire Professional Whitening by Den-Mat Holding

Reputed for being gentle on sensitive teeth and gums, the Den-Mat Sapphire Chairside Whitening system combines a 25 percent solution of hydrogen peroxide gel with a desensitizing enhancer. After these two ingredients are painted onto the teeth, a light known as a Whitening Crystal is positioned directly in front of the teeth for 30 minutes, after which both gel and desensitizer are removed. The teeth are then checked for whitening progress and, if necessary, bleached for an additional 30 minutes.

Total chair time: Approximately one hour.

Zoom Chairside Whitening

Widely used throughout the country and the world, the Zoom system features a 25 percent hydrogen peroxide gel and the Zoom Advanced Power Chairside Lamp, said to accelerate the bleaching process. Generally, the hydrogen peroxide gel is applied three times, each interval lasting 15 minutes. Immediately afterwards, a sensitivity-reducing fluoride paste-gel is applied to the teeth.

To help maintain your whitened teeth, you are given a Zoom! home-use touch-up kit, including custom-fitted whitening trays.

Total chair time: Approximately one hour.

Deep Bleaching

Deep Bleaching is not a teeth-whitening brand, but rather a multi-phase protocol involving a reversal of the usual chairside bleaching, followed by home bleaching. This technique has a reputation for whitening even the most intransigent stains (due to tetracycline or fluorosis, for example) and for maintaining optimally whitened teeth over the long haul.

Step 1

During an office visit, the dentist takes highly detailed impressions of the teeth and gumline. Based on those impressions, vinyl trays containing bleaching-gel reservoirs are custom-fabricated. Resembling the aligners used in contemporary orthodontics, these trays provide a unique fit that compresses right up to the gumline. The intention is to keep the bleaching gel sealed inside, thus preventing gum irritation and the mixing of saliva with the gel.

Total chair time: 30 minutes.

Step 2

You return to the dentist's office for a “conditioning visit.” The aim here is not to whiten the teeth, but rather to make them more permeable to oxygen.

• First, the outer surfaces of the teeth are polished with pumice powder.
• Next, two coatings of a desensitizing-conditioning agent are rubbed onto the teeth.
• Your custom-made bleaching trays are loaded with a nine percent hydrogen peroxide gel and pressed onto the teeth. Since the trays are designed in part to protect the gums, the use of retractors and rubber dams is optional – though recommended for patients with extremely sensitive gums. The trays remain in place for 20 minutes.
• The gel is suctioned out of the trays and off the teeth.
• The trays are reloaded, reinserted for 20 minutes and then removed.
• Two coatings of desensitizer are again rubbed onto the teeth.

Total chair time: Approximately one hour.

Step 3

You are sent home with a kit containing your trays, sufficient carbamide peroxide gel to be used overnight for 14 consecutive nights (when saliva flow is at a minimum and least likely to interfere with the peroxide's bleaching action) and a tooth desensitizer contained in a squeeze bottle. The goal is both to whiten the teeth and to make them more permeable to oxygen.

Step 4

Now with your teeth more receptive to the oxygenating effect of bleach, you return to the dentist's office – this time for a standard power bleaching session with retractors and rubber dam. Depending on how deeply the teeth have been bleached using the home trays, your dentist will use a nine percent or a 27 percent hydrogen peroxide solution.

Following chairside bleaching, your teeth will have been bleached to maximum whiteness.

Total chair time: Approximately one hour.

Step 5

To maintain maximum whiteness, you continue using your Deep Bleaching Trays overnight once every one to three months. If you drink red wine on a daily basis, you are advised to use the trays overnight once every two weeks.

Dentists who use the Deep Bleaching regimen say it provides permanent deep-whitening if patients follow maintenance instructions.

At-Home Teeth Whitening

When contemporary peroxide-based teeth whitening gained popularity in the early 1990s, it was limited to custom-made bleaching tray treatments that were available only at dental offices.

These whiteners set off what has become known as the “smile revolution,” and now dozens of whitening options are available for every budget and temperament – whether professionally dispensed, store-bought or sold on the Internet. Many teeth-whiteners are pre-mixed and ready to use; others require mixing at home.

The consensus is that dentist-dispensed whitening trays and whitening strips, when used as directed, can be even more successful than in-office bleaching over the long haul.

A key reason is their ongoing use, combined with the fact that small amounts of bleach remain within the tooth structure for up to 36 hours. When a new dose of bleach is applied to a tooth retaining the previous day's peroxide, its effect is greater.

Advantages of At-Home Teeth Whitening

• Long-term results: Dental professionals agree that the only way to maintain your whitened teeth is with at-home bleaching products, repeated regularly – preferably every four to six months. But lately, many dentists are advising people with very dark-stained or tetracycline-affected teeth to continue home bleaching over a period of months (or up to a year) for optimal results. What's interesting is, the newest teeth whitening strips on the consumer market are intended for five-minute use every day, like brushing or flossing.
• Variety: You have a choice of whitening trays, strips or paint-on products, as well as numerous whitening accessories.
• Convenience: You can do home whitening at any time of the day or night, for short or extended periods.
• Portability: You can also use at-home whitening strips while on the go or at the office.

Must-Knows About At-Home Whitening

Although you can get over-the-counter whiteners without a dentist's recommendation, if you over-use them or use them incorrectly, they can harm your tooth enamel and irritate your gum tissue. Also, over-bleaching can produce an undesirable bluish hue, chalky whiteness or uneven results (otherwise known as “the technicolor effect”).

Supervision by a dentist can prevent these problems. To ensure the health of your smile, see your dentist before choosing an over-the-counter tooth whitener and beginning the bleaching process. Dentists know a lot about these products and can help you choose the right one and use it correctly.

Also keep in mind:

• The stronger the peroxide formula, the more rapid its effect; the weaker the formula, the longer it can remain on the teeth safely. A low-percentage bleach used overnight every night of the week will produce about the same results as a high-percentage "day-bleach" that stays on the teeth one hour per day for seven days.
• The best time to begin at-home whitening is soon after a dental hygienist's prophylactic cleaning. This procedure removes the surface layer of plaque and grime that can interfere with bleaching.
• Dentists and oral care companies urge brushing and flossing the teeth just prior to any kind of at-home or on-the-go whitening.
• For best results, don't consume food or beverages (excluding water) for a couple of hours after whitening.

Dentist-Dispensed Take-Home Whitening Trays

According to dental professionals, the best bleaching results come from dentist-dispensed take-home kits – particularly those that are used over extended periods. These kits contain higher percentages of bleach than over-the-counter kits and typically consist of:

• Custom-fitted application trays made of a flexible plastic material. Custom trays offer several benefits:
  • They help ensure that the bleach stays in contact with the teeth, for maximum whitening.
  • They help prevent saliva from coming into contact with the bleaching agent (which can dilute its strength).
  • They minimize the amount of bleach that can dribble onto (and potentially irritate) the gums.
• Bleaching compounds are either pre-loaded into the trays or stored in syringes and added to the trays just before use. In many cases, your dentist can fine-tune the bleach concentration and add a desensitizing agent to use before or after application. Generally the kits provide enough gel for one two-week treatment per year, plus one- or two-day touch-ups every four to six months.

The following tray-bleaching systems are what most dentists dispense:

Discus Dental Nite White and Day White ACP: These are the only take-home whiteners with amorphous calcium phosphate (ACP), a proven enamel re-builder, and sensitivity-reducing potassium nitrate and fluoride.

Nite White is available in various hydrogen peroxide concentrations, for either overnight or twice-daily use. Ask your dentist which concentration and application are best for you.

Discus Dental Nite White Turbo: This is the fastest Nite White system, containing a mint-flavored, chemically accelerated 6 percent hydrogen peroxide formulation. It is intended for overnight use, two to four hours twice a day, or one to two hours a day if you are sensitive to bleach.

Discus Dental Zoom! Weekender Kit: This fast-acting whitening system has a 6 percent hydrogen peroxide gel and a time-release booster agent that enhances bleach penetration. The Weekender Kit is intended for overnight use, two to four hours twice a day, or one to two hours a day if you are sensitive to bleach.

Opalescence by Ultradent: Incorporating a viscous carbamide peroxide whitening agent known for its staying power over extended periods of time, the Opalescence gel also contains a patented mix of sensitivity-reducing potassium nitrate and fluoride. Pre-packaged in syringes, the gel is inserted into the custom-made trays before each use. Four concentrations of carbamide peroxide are available for use during the day or overnight.

Opalescence kits come in mint, melon and flavor-free formulas. Best results will likely appear after 10 days of directed use.

Opalescence Trèswhite Supreme: This innovative, one-size-fits-all system is designed for those who want a quick, convenient and relatively inexpensive whitener, with no wait for custom-made trays. Many people use this system while traveling or just before a major business meeting or social event.

Trèswhite has a two-layer tray system that guarantees automatic alignment. The delivery trays are pre-loaded with a membrane-like inner tray coated with a 10 percent hydrogen peroxide whitener containing the same sensitivity-reducing mix of potassium nitrate and fluoride as is found in Opalescence systems with custom-made trays.

The wear time for Trèswhite is 30 to 60 minutes, once a day. Packs of Trèswhite Supreme (10 uppers and 10 lowers), for use over the course of five to 10 days, are available in mint, peach and melon flavors.

Whitening Strips

Coated with a whitening gel, these thin, flexible membranes are designed to conform to the shape of the teeth. They are very convenient and easy to use – no mixing or molding is required. What's more, they are unobtrusive enough to be worn on the job or while commuting or shopping.

However, whitening strips are less effective than trays for removing between-the-teeth stains and are not suitable for crooked teeth. In addition, saliva can more easily find its way beneath whitening strips, diluting their potency. Some whitening strips aren't long enough to cover a wide smile, and they tend to slip and slide.

Crest Whitestrips Supreme, containing 14 percent hydrogen peroxide – the highest dose currently available in whitening strips – are dispensed at dentists' offices. These strips are wide enough to cover up to six teeth.

Brush-On Whiteners

Pens with brush-on or foam-tip applicators provide what has been billed as fuss-free instant whitening. Used directly after meals or in daily regimens, as alternatives to whitening trays and strips, these whiteners are often considered instant "antidotes" to new stains from food, especially just-consumed red wine.

But dental professionals are divided as to the effectiveness of paint-on whiteners. Some consider them useful adjuncts to in-office or tray bleaching. Others have yet to see any meaningful results with these whiteners.

Whitening Toothpaste

Technically speaking, all toothpastes are whitening toothpastes, since they remove surface plaque and debris. But only a few contain key whitening ingredients: chemical bleaching agents and abrasives in high concentrations.

When used regularly, these toothpastes may offer backup support for tooth whitening. Of course, given that brushing time is limited to a minute or two, that support is minimal. But since we all brush every day, some consider whitening toothpastes to be potential whitening enhancers.

Toothpastes with Peroxide

Because toothpaste foams all over the mouth and is swallowed, the percentage of any bleach it contains is low, to avoid irritation.

Toothpastes with Abrasives

Most toothpastes clean the teeth with finely ground abrasives such as silica, aluminum oxide, calcium carbonate and baking soda. Whitening toothpastes contain more of these abrasives – though the paradox here is that overuse can cause more stains and can also dull the surface of dental crowns and veneers.

Whitening Floss

Floss may seem like an unlikely part of the tooth-whitening regimen, particularly as it is in contact with the teeth for only a second or two. But over the long haul, using whitening floss daily may assist with stain removal in the narrow space between the teeth, an area that even in-office bleaching has a hard time reaching.

Whitening floss differs from standard dental floss in its use of mild abrasives, typically silica.