Skip to main content


I get a lot of questions from my patients about teeth whitening. Should I do it? Which whitening method is the best for me? Etc. Here are some of the most common questions received and my suggestions. I hope that at least one of the answers pertains to your situation, and you find it helpful in making your decision whether to whiten your teeth, and if so, which method to choose.

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 is to determine the cause of the tooth discoloration. 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.

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. The most common and thoroughly researched bleaching substances are 10% carbamide peroxide (used at home in mouth trays) and 35% hydrogen peroxide (used in a dentist’s office). 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. 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.

If my teeth do become sensitive during the whitening process, is there anything I can do about it?
To those who already know that 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?
It is important to realize that 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?
Even though we do not perform many bleaching procedures on children, the research shows that 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. Many dental professionals 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 tends to be less of an issue with younger people. In adults, teeth bleach well as long as there is no significant root exposure. Individuals over 45 generally appear a decade younger with whiter teeth.

What are the different procedures used to whiten teeth, and how do they compare in terms of safety, effectiveness and total treatment times?
There are three options: in-office whitening done by a dentist, at-home bleaching with custom-made flexible plastic trays, and over-the-counter 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. Comparing 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.

Many dentists agree that a 10% carbamide peroxide treatment in a custom-fitted tray is generally the safest, most cost-effective, best-researched whitening treatment available. Most importantly, 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?
The research has been divided on this one. 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, aside from additional expense, is that there can be an increase in tooth sensitivity.

I have a single, dark tooth. What can I do about it?
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, 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), a single-tooth bleaching tray 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, optimal outcome has been attained. 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?
This is an important discussion I often have with my patients. It is important to know that tooth-colored composite (plastic resins) or ceramic (porcelain) tooth restorations cannot be lightened with bleach. They will 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.

Once I get my teeth as white as I want them, how long should it last?
This will vary among individuals. It is important to realize that 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?
Yes, they are things you can do to prolong the results of teeth whitening procedure. You should 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. It is important to remember that all aspects of tooth whitening are best performed under professional supervision.

Dr Arash Asil DDS, is a dentist at Smile Design Dental Group in San Clemente, CA. Call (949) 481-2000 or click here to make an appointment.