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Important Teeth Whitening Questions Answered

If you are thinking about getting your teeth whitened at your dentist's office or doing it yourself at home, this is a must-read!

By Dr. Van B. Haywood

This article is endorsed by the
American Academy of Cosmetic Dentistry.
Teeth whitening questions answered.

If I don't like the color of my teeth, how can I tell if whitening would be a good option for me?

The first step in deciding whether or not to whiten teeth should always be a proper dental examination — with x-ray pictures — to determine the cause of the tooth discoloration. This is the best context in which to explore whitening options, with the person who is in the best position to advise you: your dentist. The optimal, most natural-looking tooth shade is always the one that creates a match between the whiteness of the teeth and the whites of a person's eyes.

Is there any reason why I shouldn't try whitening my teeth?

The pre-bleaching exam may reveal a need for a particular treatment, before or even instead of bleaching. For example, there are several causes for discoloration — abscessed teeth, decay, and root canal problems, to name a few — for which bleaching will mask but not resolve the problem. There are also some aesthetic considerations, such as how much of your teeth and gums show when you smile. Typically, short teeth and a gummy smile do not look better with bleaching because whiter teeth will accentuate the gummy smile. Also, exposed tooth roots don't bleach, so if you have root exposure, your results won't be ideal. In either of these cases, you may want to consider other cosmetic options.

Applying teeth whitening solution with brush in dental office.
In-office whitening procedures begin by protecting your lips, gums and mouth, leaving only your teeth exposed for the application of the whitening gel.

Can whitening damage teeth?

A large body of research on bleaching has determined that low concentrations of peroxide, from a reputable source, are safe if used as directed, after a proper dental examination. However, tooth sensitivity is a common side effect of bleaching. Solutions that are more acidic can etch the enamel from the teeth, especially if used for long periods of time, so are to be avoided. The most common and thoroughly researched bleaching substances are 10% carbamide peroxide (used at home in mouthtrays) and 35% hydrogen peroxide (used in a dentist's office). Carbamide peroxide is actually hydrogen peroxide plus urea. Carbamide peroxide products remain active longer — for up to 10 hours and lessen acidity to a level where the enamel is not affected and the person cannot get tooth decay. Hydrogen peroxide may come in stronger concentrations, but only stays active for up to an hour and is more acidic, so should not remain on the teeth for extensive lengths of time. There are carbamide peroxide materials for both at home and in the office treatment, as well as hydrogen peroxide materials for in the office and at home treatment. The concentrations vary, and determine the treatment time and technique. Also, if a high concentration of material is being used, your dentist must take steps to protect your gums from coming into contact with it. Since peroxide even at a low concentration can burn inflamed gum tissue, your gums need to be healthy prior to bleaching. Waiting two weeks after having the teeth cleaned is advisable, as well as using a soft toothbrush with the appropriate brushing (not scrubbing!) technique.

Before teeth whitening.
Teeth yellow with age; a variety of foods and beverages can also cause darkening and discoloration.
After teeth whitening.
A smile can be returned to brilliance with today's teeth whitening products.

If my teeth do become sensitive during the whitening process, is there anything I can do about it?

First of all, if you already know you have sensitive teeth, there are precautions you can take before beginning the bleaching process. Brushing with a desensitizing toothpaste containing potassium nitrate for two weeks prior to bleaching can reduce sensitivity. Using potassium nitrate during the bleaching process (in the bleaching tray) can also help, as can reducing the frequency of bleach application, the duration of treatment, and taking breaks from the continuous application of the bleach.

Are all teeth susceptible to whitening?

All teeth do not reach the same whiteness. Each tooth has its maximum whiteness beyond which it will not whiten, regardless of the technique or material used. Peroxide goes through the enamel (the outermost layer) and dentin (middle layer) to the pulp (innermost layer) in 5 to 15 minutes. It changes the genetic color of the dentin and the enamel, and removes stains. Most teeth get more opaque upon bleaching, but a tooth that's already translucent can become more translucent and may not appear to whiten at all. In these cases, a tooth-colored composite (filling material) placed on the tongue side of the tooth can improve its appearance.

Is age a factor?

Generally, you can bleach your teeth at age 10 or older, as most of the front adult (permanent) teeth are in by that time. Baby teeth are usually milk-white already; the only reason to bleach them would be if they suffered a color-changing trauma but were not diseased. I believe that if a young person has discolored teeth, it is better to whiten them than wait and have the child deal with the embarrassment of the discoloration. Sensitivity is seldom a problem with younger people. And older people's teeth bleach well as long as there is no significant root exposure, as mentioned earlier. I have found that individuals over 45 generally appear 10 years younger with whiter teeth.

Professional In-Office teeth whitening.
In-office teeth whitening can achieve an approximate 6-shade improvement in 3 (dental) office visits.
Take home teeth whitening.
At-home systems using professionally made dental trays require approximately 7 nightly applications to produce a 6-shade improvement.
Over the counter teeth whitening.
At-home whitening strips require 16 daily applications to produce a 6-shade improvement.

What are the different procedures used to whiten teeth, and how do they compare in terms of safety, effectiveness and total treatment times?

Basically there are three options: in-office whitening (done by a dentist), at-home bleaching with custom-made flexible plastic trays (called nightguard vital bleaching), and over-the-counter (OTC) products. Within each of these classes the technique can vary, as does the concentration of bleaching solutions and duration of treatment. The in-office bleaching solutions are the strongest, so precautions must be taken by the dentist to protect the gums from coming in contact with them. As for comparisons among the three options, one study found that a six-shade change required either: three in-office applications of 38% hydrogen peroxide; one week of 10% carbamide peroxide used at home nightly in a custom-made tray; or 16 daily application of 5.3% hydrogen peroxide on a strip. A 10% carbamide peroxide treatment in a custom-fitted tray is generally the safest, most cost-effective, best-researched whitening treatment available. Of course, your own preferences, lifestyle, and finances will also come into play when making a treatment choice. It's important to keep in mind that all three of these options should eventually achieve the maximum whiteness allowed by the tooth given enough time to work.

Do lasers/lights have any effect on the bleaching process?

This has not been proven. The outcome is the same with or without the light. The light may provide some faster initial rate of change in the first few days, but it is the peroxide that is doing the bleaching. Most likely, they only give the appearance of whitening as a result of dehydration or drying out of the tooth. The main problem with lights, besides additional expense, is that there can be an increase in tooth sensitivity.

Dark tooth before teeth whitening.
Trauma is often responsible for a single tooth becoming darkened.
Dark tooth after teeth whitening.
Teeth whitening can dramatically enhance a smile.

I have a single, dark tooth. What can I do about it?

The first step is to determine why the tooth is dark, as that is often an indication of dental disease, which may require additional or different treatment. Once the cause of the discoloration is determined, there are two techniques that can work well for an individual darkened tooth. If the tooth has become dark because it needs a root canal or has already had one, it can actually be bleached from the inside. Your dentist or an endodontist (root canal specialist) will need to do this bleaching procedure, which requires making a small opening in the tooth through which to bleach the tooth from the inside.

If it is still a living tooth (and does not need a root canal), your dentist can design a single-tooth bleaching tray that will keep the bleach away from your other teeth, in order to create the best color match. Once the dark tooth matches the rest of the teeth, that may provide the best cosmetic outcome. If the single dark tooth becomes lighter than the unbleached (other) teeth, then all the teeth can be carefully whitened together if needed.

Does bleaching have any effect on existing dental work, such as fillings, veneers or crowns?

Tooth-colored composite (plastic resins) or ceramic (porcelain) tooth restorations can't be lightened with bleach. They remain the same color. Therefore, you will have to consider what your smile will look like if your natural teeth get lighter but your restorations do not. This is a good topic to discuss with your dentist, who can run through the options in your particular case.

Once I get my teeth as white as I want them, how long should it last?

This will vary among individuals. No bleaching method can whiten teeth permanently. Typical results vary from six months to two years. However, some people's teeth remain white for over 10 years with no touch-up treatment.

What can I do to make the results last as long as possible?

Keep up with your regular oral hygiene routine at home and your professional cleanings at the dentist's office. Avoid tobacco and beverages that stain, such as red wine, tea and coffee. You can also consider a bleaching touch-up once or twice a year at home or at the dentist's office. Your dentist can advise you about maintenance protocols that best serve your particular needs. It is important to remember that all aspects of tooth whitening are best performed under professional supervision.