Questions and Answers about Teeth Whitening

Actual tooth whitening case done by Dr. Le

Actual tooth whitening case done by Dr. Le

Does bleach weaken your enamel?  Does it really make your teeth more sensitive?  Do you do Zoom or Britesmile?  We answer these and over a dozen more frequently asked questions on tooth whitening.

How was tooth whitening invented?

An orthodontist wished to use hydrogen peroxide to control plaque accumulation on his patients’ teeth.  One “side effect” of leaving hydrogen peroxide on teeth was that they became whiter.  This is how a multi-billion dollar industry was born.

Why is tooth whitening also called bleaching?

Bleaching is just another term for using an oxidizing agent.  In your laundry machine, the oxidizing agent is most often sodium hypochlorite, a.k.a. Chlorox or household bleach.

The two most popular oxidizing agents in dental tooth whitening are hydrogen peroxide and carbamide peroxide.  Carbamide peroxide takes roughly three times as much concentration to equal the effect of hydrogren peroxide, but is more commonly used because of the promise of less sensitivity.

Does bleach weaken your enamel?


Most bleaching gels have slight to moderate acidity in order to help in the whitening process, and to improve shelf life.  (drinking Coke or even diet Coke is much more acidic than typical whitening gels.)  Acid temporarily dissolves calcium ions from the enamel.  This loss is usually temporary, and the saliva starts rebuilding the enamel as soon as the gel is removed.  (If you suffer from dry mouth, or are prone to cavities, consult with your dentist before teeth whitening, as your saliva may not self-repair enamel as well as the average person’s)

Some research shows that there is no significant change in enamel hardness.  Others say there is a temporary, slight decrease in hardness with certain types of gels.  Of course, most of these studies were done on extracted teeth on a lab bench–what scientists call in vitro.  Clinically, I haven’t been able to discern a difference, and people with bleached teeth don’t seem to fracture their teeth any more or less than those who haven’t.

The only practical advice I would give is to use a soft bristled toothbrush with water and NO TOOTHPASTE to clear bleaching gel off your teeth after each home whitening session..  If the enamel is softened by the bleach, using toothpaste, which is full of abrasive polishing grit, would accelerate erosion.

Why should I stop drinking coffee, colas and red wine while whitening?

All whitening gels have slight acidity which makes teeth more porous to bleaching agents such as peroxide.  This also makes them more porous to external stains, such as coffee, colas and red wine.  You can easily undo your whitening results by staining your teeth.  An easy rule of thumb for what foods and beverages to avoid: If it will stain a white shirt, it will stain your white teeth.

To counter the accumulation of stain, we recommend a whitening toothpaste and whitening toothbrush (the ones with the silicone polishing inserts) every morning and evening while whitening.  After you stop whitening your teeth, the enamel rebuilds itself back to normal.  You can resume your normal eating and drinking 1-2 weeks after you stop whitening.

Do strawberries really whiten teeth?

The internet myth that just won’t die is that eating strawberries will whiten your teeth because they contain malic acid, or malate.  Let’s just consider the basic chemistry.

Any brightly colored fruit is the result of high concentrations of anti-oxidants.  Teeth whitening is the chemical OXIDATION of enamel.  So can you really OXIDATE tooth structure with something high in ANTI-oxidants?  No, anti-oxidants universally STAIN things.    Spill laundry bleach on a beige carpet, and what happens?  It oxidizes the carpet, turning it white.  Spill strawberry juice on the carpet, and it stains it red.  No amount of scrubbing strawberries on that beige rug will make it any whiter.  Ever.

Our teeth are relatively stain resistant because enamel is very smooth and hard.  Thank goodness, because strawberries are delicious and nutritious.  Just don’t count on them to get your teeth any whiter.

Does tooth whitening make my teeth more sensitive?

Yes, teeth whitening commonly makes teeth more sensitive.  The effect usually lasts through the duration of bleaching treatment, then another week or two.  The amount of tooth sensitivity during whitening depends on many factors:

  1. Your teeth: If your teeth are more sensitive to begin with, you have a greater chance of having sensitivity when whitening your teeth.  People with receded gums, gum disease, untreated grinding/clenching habits, thin/poor quality enamel and other factors are more likely to have sensitive teeth without any dental treatment.
  2. The concentration of the gel: The stronger the whitening agent in the gel, the more sensitive your teeth may be.
  3. Desensitizing agents in the gel: fluoride and potassium nitrate are two commonly added ingredients to decrease sensitivity. More recently, bleaching agents are including calcium and/or phosphate in an effort to remineralize the teeth or to decrease sensitivity.
  4. Duration of exposure: How long does the bleach stay on the teeth? Is it a one hour treatment?  Is it for one hour in the office, or overnight, or a few hours a day?

Generally speaking, tooth whitening is a balance between faster, more profound results and more sensitivity.  You can also minimize sensitivity by using a sensitivity toothpaste such as Sensodyne, or a high-fluoride prescription toothpaste, which you can obtain from our office.  If you’re willing to compromise on the final result (or the time it takes to get there), you can use bleaching gel for less time, though 30 minutes is probably a practical minimum.

How many shades will I improve?

Tooth whitening is not predictable because everyone’s teeth are so individual, and because different dentists use different shade guides.   People with yellow-tinted teeth tend to have better results than people with gray-tinted teeth.  If you have a line across your teeth from childhood metal or antibiotic exposure, whitening may not completely resolve the problem; veneers may be necessary.

How white can I get it?

We generally recommend that you whiten your teeth no more than the whites of your eyes.  We feel that rule-of-thumb gives a natural, healthy look.  Your teeth should not enter the room before you do.  On the Vita Classic scale, we usually do not encourage anything beyond shade B1.  We have recently purchased a new bleaching shade scale for a few of our more “ambitious” whitening patients.  These 3 additional shades do not exist in nature, but are sought after by many patients.

How long does the new color last?

The faster it gets whiter, the faster it reverts.  Take home, two week treatments are best.  Just like getting a tan or losing weight, the slower you go, the longer it lasts and the safer it is.  As a bonus, you can use much lower strength gels, which decrease your risk of sensitivity and provide a longer lasting result.

One hour treatments are known for their rapid whitening, but also for moderate to severe tooth sensitivity and rapid rebound.  I call this “bungie bleach” because of the marked bounce back in whiteness.  You can greatly reduce rebound by bleaching at home for two weeks immediately after a one hour whitening treatment.

Do you do Zoom or Britesmile in your office?

Several well publicized whitening systems (Zoom2, Britesmile, etc.) supplement one hour of professionally applied, high strength whitening gel with high powered visible or UV light lamps.  The claim is that the UV and/or blue light catalyzes the oxidation reaction.  Bleaching lights don’t really work: In several incidences, if you bleach on both sides of the mouth, tin foil on one side, illuminate the other side, and then leave it for an hour, both sides come out the same!  The foil covered side is exactly the same color as the illuminated side.  In fact, the bright lights may harm teeth by heating up the pulp to unhealthy temperatures, and UV light in high doses is a known carcinogen.  Who pays for these expensive lights?  You, the consumer…in the form of inflated fees.

CRAnews, the Consumer Reports of dentistry, showed that  that even with our highest power resin curing lights (far stronger than the whole mouth bleaching lights), there is no significant increase in the breakdown of peroxide.  (Warning: it’s a fairly technical article).

Numerous dentists and journals have tried this, and the results are always the same: the light-covered area is just as white as the light-exposed area.  We will not participate in this mass deception of the public no matter how commercially profitable it is.  It’s all in the gel.  Just say no to bleaching lights.

Do white strips work?

White strips actually work, but work best on those with straight teeth.   They are also not wide enough for all smiles.  Because the concentration of the gel can be lower, they may take longer than professional products available through the dentist.  With that said, Procter and Gamble has recently increased the strength on their premium products to levels very close to dental strength products.  No strip, however, can provide the fit, comfort or isolation that a dentist-made custom tray can.

I don’t have a problem recommended white strips, because they are much more effective than any of the other over the counter alternatives.  You should also consider our Opalescence Go! kits, which don’t cost much more, fit better, and use a stronger gel.

Do whitening toothpastes, toothbrushes, and mouthwashes work?

Toothbrushes (and toothpastes) that claim to whiten more usually do so by adding extra abrasive.  For people with healthy brushing habits, ADA considers whitening pastes with the ADA seal to be safe for everyday use.  I would tend to agree, unless you are heavy handed, or have sensitive teeth–whitening toothpastes may exacerbate the problem.  Professional tooth whitening is a safe, much faster way to whiten most teeth.  Whitening toothpastes may be a good way to minimize the buildup of external stain on teeth between dental visits.

Other products use chemical agents such as hydrogen peroxide.  Hydrogen peroxide, in high strength, will burn gums and soft tissue.  In order to make a product safe for consumer use without dental supervision, over the counter hydrogen peroxide products typically use much a lower strength.  In the case of toothpaste or mouthwash, there usually isn’t enough concentration or exposure time in the mouth to make a meaningful difference.

Will my fillings change color, too?

If you have fillings or caps, they don’t change color with teeth whitening.  Only natural teeth whiten.  There are anecdotal reports of extreme strength bleaching protocols changing the color of fillings, but these regimens also cause extreme sensitivity, requiring significant prophylactic doses of pain medication.

A more sensible approach is to whiten the teeth to the desired shade, then replace any fillings that no longer match.  Replacing the fillings before whitening is not recommended, as your final shade is not entirely predictable.

If I’m getting veneers anyway, do I still need to bleach?

In order for veneers to look their best, they should be translucent, (show light through them) just like natural teeth.  That means they tend to show through the color underneath.  You should always whiten all the surrounding teeth anyway, so that you can have a brighter smile overall.

I have a gray tooth from a root canal.  What can I do to fix it?

Several things can be done, but it may take a combination of them to get good results.  Non-vital teeth are the hardest to whiten, and no treatment is guaranteed to produce a satisfactory result.  As always, consult with a  dentist to see which, if any, of these treatments are appropriate to you:

  1. If the dentist who filled the root canal used silver filling, then you may be able replace the internal silver with bright white filling. (sometimes silver fillings blacken the teeth all the way through, which is nearly impossible to fix)
  2. Whitening trays: A custom tray is made to apply bleaching gel to the teeth.  Once the other teeth are a satisfactory color, continue applying gel only to to the problem tooth.  This has very limited success.
  3. Externally whiten the tooth: We isolate the problem tooth and apply a maximum strength peroxide to it for 45 minutes.
  4. Internally whiten the tooth: The tooth is isolated, the top of the root canal filling is opened, and bleaching agent is placed inside the tooth for 45 minutes.  Then it is removed and the tooth is refilled.
  5. Walking Bleach: the most common treatment used by dentists. The tooth is opened up, bleaching agents are placed in the mouth, and a temporary filling is placed in.  The bleaching is replenished periodically until the desired result is produced.
  6. Veneer the tooth
  7. Place a cap over the tooth – this is the only guaranteed method, but it is the least conservative option, as the tooth has to be shaved down to accommodate a crown. Only use this option as a last resort.