Professional teeth whitening all started with the teeth whitening tray.
Before the 1990's, it was the only option for a teeth whitening treatment and was only available  as a "in-office" treatment.
Dentist then began to offer a "at home version" of the whitening tray.
This was not available in stores, only at your dentist, but this first "at home tray" started the teeth whitening phenomenon.
  This dentist-supervised  "at home"  version of the teeth whitening tray has a few advantages over the in-office professional treatment.
The bleaching product contains  a much lower dose of peroxide, witch lowers the chances of undesired side effects.
And of course, since the treatment does not require the presence and time of a professional, it is  much less expensive.
Nowadays, you can easily purchase a whitening tray outside the dentist's office.
The one sold by your dentist will be custom fit to your teeth.
The tray found at the store, of course, will not.
The variety of whitening trays offered in stores is endless, but the most common complaint is discomfort.
(you will have to wear them up to twice a day for 2 weeks), product leaking, and the upper tray falling.
It will still whiten you teeth but the results may not be even.
The best teeth whitening trays are found at your dentist, but another option for a good fit is thermoforming tray.
These trays work like the custom fit tray but cost significantly less.
You may like to try the moldable thermoforming bleaching trays to get the best value from your money spent.