Americans spend millions of dollars each year to whiten their teeth. This money is spent on both dentist teeth whitening systems and off the shelf teeth whitening. So, let's take a look at the advantage of dentist teeth whitening systems:

Advantage one: the bleach is stronger

The bleaching agent's strength varies from procedure to procedure, but no matter what dentist whitening system you use, it is going to be much stronger than that of an over the counter, off the shelf teeth whitening system.

Normally the bleaching agent contained in an over-the-counter whitening kit is of a lighter level, as anyone can use it without posing serious risk to them self. For example, it might have around 10% of carbamide peroxide, or if it is a really strong, high profile off the shelf system it may even reach the 22% of carbamide peroxide. However, on the other side, with dentist or professional whitening products you get up to 43%, and generally a minimal of around the highest level from off the shelf products. The carbamide peroxide is strong, and thus at this level it is to be applied under the strict eye of the dentist only. So, even if you wanted to, you would not be able to get a stronger bleach without going through a dentist.

Advantage two: form of application

For the best forms of over the counter whiteners you use mouthpiece trays. However, the dentist can provide a very precise impression of your teeth and produce a customized tray which will exactly fit your mouth, and thus you get more uniform whitening. Often times with off the shelf whiteners you get spots where the bleach did not have direct contact with the teeth, and thus was not as effective.

A dentist is very precise in their molded mouth piece trays, and with this kind of precision, whitening gel will have direct contact with the teeth. So you get a better whitening all around through the professionally made mouthpieces.

Another problem with mouthpieces that are made in shops to fit standard sizes and are not specifically designed for your specific mouth, is that this causes imprecise application of the gel which not only leads to inconsistencies, but in turn can irritate the gums as the gel slips out of its normal path. So, it could be very painful. Dentist teeth whitening systems do not have these problems.
 
Advantage three is the dentist can take additional protective measures if needed

When you go in to get your teeth whitened at the dentist office, the dentist protects the gum with a gel or uses a shield, sliding it over the teeth as protection against bleaching agents. You can't get this in over-the-counter bleaching.
 
Advantage four is simply that it is professional

When you go to a dentist to get your teeth whitened it looks better faster, lasts longer, and is basically guaranteed to go well because he or she is a professional. The process is all done under supervision, which provides another level of safety in the process.

Advantage five is the dentist can determine the cause of staining and thus how best to fix it.

The causes of stains and its appropriate treatment are easily determined by a dentist, whereas if you choose over the counter or off the shelf whitening you are up to your own means to figure out what the best way to get rid of coffee stains is. With dentist teeth whitening systems you get a professional indication on the frequency and level of treatment required for restoration, and follow-up of the whole process.