There are some areas of consideration and concern when it comes to the use of over-the-counter teeth whitening products. Listed below are links to discussions about some of them:
The increased availability of over-the-counter teeth whitening products has removed a valuable resource from the teeth whitening equation, that being the supervision of the process by a dentist. Just because you are considering using an over-the-counter whitener doesn't mean you shouldn't or can't make mention of this fact to your dentist.
No one could possibly know more about the subject of teeth whitening in general and specifically how it relates to your precise situation than your dentist. By having your dentist involved in your teeth whitening decisions they can help you address and resolve issues that could lead to product abuse. Some of these issues are:
Some people simply do not have a concept of what constitutes a natural shade of white for teeth. And just as a person suffering from an eating disorder might never see themselves as being too thin, some people who bleach their teeth never see them as being too white. And this situation can lead to teeth whitening product abuse.
Sometimes a person will compare their own smile to images of humans they see in films, on TV, or in magazines. No doubt these people already know (but possibly don't realize) that so many of the commercial images we see are "air brushed" versions of reality. The smile we are visualizing doesn't really exist.
Even in those cases where the images of smiles we see are real you can't assume that what you see is just the result of teeth whitening treatment. Many times a person's smile has been altered by dental work. And just as people sometimes take cosmetic surgical procedures to the extreme point of reaching comic physical proportions, a person's teeth can be abused in similar fashion with dental work. And no over-the-counter teeth whitening process can, nor is intended to, provide this same type of dramatic change.
When it comes to the unsupervised use of over-the-counter teeth whitening products "more" is not necessarily a good thing. It is not the intention of the makers of over-the-counter teeth whitening products that their whiteners will be used for a prolonged and continuous duration. These are not the conditions under which the safety evaluations of these products have been conducted. These are not the conditions under which the effectiveness of these products has been studied either.
No over-the-counter teeth whitening product is sold where the manufacturer expects the user to use the product for weeks and months on end before the user will find the product to be effective. The manufacturer will have evaluated their product's safety and effectiveness and they will have incorporated their findings into their product's instructions. These instructions need to be followed. They are there for a reason, your protection against product abuse.
This does not mean that all persons who use over-the-counter teeth whitening products as directed will get the results the manufacturer suggests they can get, nor the results that they desired. What this does mean is that quality over-the-counter teeth whitening products can be expected to produce good results for many, and possibly even most, people. If using the product as directed does not produce the results you wanted you should once again seek your dentist's advice, this time for further treatment suggestions or treatment alternatives.
Of course there is no absolute answer to this question. There are however some guidelines you might develop.
When we look at others our mind has a general expectation as to what we anticipate we will see. That is, there is a spectrum of tooth coloration that defines the range of what we interpret as being normal and natural. (Dentists use "shade guides" to quantify where in the range of normal a person's tooth coloration lies.) Some persons will have teeth that are inherently lighter in shade than others. But if a person's tooth coloration falls outside of the range of what we consider normal, say too white, then their appearance takes on an unnatural, sometimes even freakish, look.
This range of color that we interpret as appearing natural will vary from individual to individual. Factors such as skin tone and hair color can have an influence. Shades that appear natural will also change for a person with each passing decade. Since it is characteristic that a person's teeth will darken with time, clearly a 60-year-old would be expected to display a different tooth coloration than a teenager. Think how ridiculous a pop idol's smile would look on an elderly head of state.
Now, look around at those who surround you. What do you see? (Actually the first thing that we see is that no one around us looks anything like the model on the whitening product's box. That alone should be a tip off that often the standards that are put in front of us as being the ideal should probably instead be categorized as extremes. Anyway, enough of our bias now back to the text...) What is the range of whiteness you notice with other people's teeth?
When you look at a person's face there are only two features that have a strong white coloration, their teeth and the whites of their eyes.
You might use these two reference points as a basis of comparison.
For us, we personally think that if a person's teeth are whiter than their eyes that it is rather obvious that they have whitened their teeth.
But maybe that is the appearance you are looking for.
It would be our opinion that when aspiring to a tooth color that it's fine to aim for a coloration that lies at the lighter end of the "normal" range rather than the darker. But it's necessary to keep your goals realistic. And these more "realistic" degrees of whiteness will be the ones that over-the-counter products are intended to help you achieve.