When won't teeth bleaching work?
The results that a tray-based at-home teeth whitening system can produce are not always easy to predict. Most certainly some types of tooth discoloration are more resistant to lightening than others. Your dentist, as part of their initial examination, will need to determine the most likely cause of your tooth staining. Having done so they can then convey to you what type of whitening results they think can be achieved.
Attempting to bleaching teeth to an unnatural level of whiteness can be expected to fail.
Your dentist will not be able to unconditionally guarantee that you will be pleased with the outcome of your teeth whitening efforts. This is because many people have a very unrealistic idea of what constitutes a natural shade for teeth.
Some people will compare the color of their teeth to those people they see featured in films, on TV, or in magazine advertisements. In fact, the shade of many models and actors' teeth fall into the realm of "unnatural." The extreme shade you see has either been achieved by a means other than by bleaching (such as by placing dental crowns or porcelain veneers) or else never existed at all and instead was created by doctoring a picture.
Sometimes, in an attempt to achieve an unnatural shade of tooth whiteness, a person will exceed the treatment recommendations that accompany the bleaching system they are using. This type of whitener abuse can put the person at risk because they are using the bleaching agent in a realm beyond where the safety of the product has been evaluated.
The whitening results you achieve may not be as dramatic as the results you were hoping for.
Even people with realistic whitening goals may be disappointed with the results they achieve with teeth whitening treatments. The baseline color of some people's teeth is just naturally darker than others and therefore their teeth have less inherent potential to lighten. Additionally, some types of tooth staining are simply more resistant to lightening than others.
A patient's motivation and level of compliance with the whitening protocol's instructions will play an important part in the overall out come of a case. But even in those situations where motivation and compliance are high, a point will be reached where further treatments do not seem to provide further whitening results. And this endpoint may or may not be the one the patient was hoping for.
At-home tray-based teeth whitening cannot be expected to lighten existing dental work.
From a practical standpoint, teeth bleaching treatments cannot be expected to make a change in the color of existing dental work. Our "Effects of peroxide whiteners on existing dental work" page discusses some research findings related to the effect (both color and structural) that peroxides can have on various types of dental materials. In most cases, a person's teeth should be whitened first and then afterwards their dental work replaced so to match the new shade of their teeth.
Before the bleaching process is begun a person should have discussed with their dentist how much post bleaching dental work will be needed. The time and cost associated with replacing dental work can be significant.
There can be an exception to the rule that existing dental work cannot be lighted with whitening treatments. Some types of dental restorations are, at least to some degree, translucent. If this is the case then if teeth whitening treatments can lighten the color of the tooth structure that lies underneath these translucent restorations then the restoration itself may appear lighter. This approach can be used in an attempt to lighten porcelain veneers. Less predictably, teeth whitening treatments might affect the color of white dental fillings.
Difficulties associated with whitening teeth that have gum recession.
Once a person has experienced gum recession that portion of each tooth's root surface that is now visible will have an appearance that is somewhat darker than the rest of the tooth. This is because root surfaces are not covered by enamel but are instead composed of another, naturally darker, material (dentin).
Teeth whitening treatments won't effectively lighten dentin. This means that the color of the root portion of the tooth (which shows where the gum recession has occurred) will not change noticeably as a result of your bleaching efforts.
