Teeth whitening
In recent years, teeth whitening has become a huge phenomenon. A whiter, brighter smile is one of the first things that people notice about your appearance. Whiter teeth make us look better: younger, more attractive, more confident. This is why men and women of all ages are now opting for teeth whitening systems to improve their smile.
There are a number of factors that determine the success of any teeth-whitening product, including the present state of your dental health.
That is the most important reason to consult a dentist if you are planning on whitening your teeth.
You can get lots of information by consulting the Internet, for example:
http://www.teethwhiteningreviews.com or Wikipedia

Tray Whitening is now considered as “the gold standard” due to a more predictable result that lasts for a longer time and is easily maintained by touch-ups.

The higher concentration formulas can most definitely cause teeth sensitivity. There is also a difference between whitening brands. A study done by
Dr. Wm Browning of Medical College of GA tested the sensitivity factor of Opalescence PF 10%, NiteWhite Excel 2Z 10% and Rembrandt XtraComfort 10%. The study found that all exhibited some degree of sensitivity but that Opalescence users had less sensitivity and for a significantly shorter period of time.

How does it work? :
The oxidizing agent (carbamide or hydrogen peroxide) penetrates the porosities in the rod-like crystal structure of the enamel and oxidizes stain deposits. Over a period of time, the dentin layer, lying underneath the enamel, is also whitened.
It is important to take into consideration that teeth whitening does not change the colour of fillings and other restorative materials.

Is it safe?
: The answer is both yes and no. Yes, if you use the treatment the way it is supposed to be used, and no, if you use it in excess or do not follow the instructions. However the ingredients used in teeth whitening products are safe, if used in proper quantities and for the right amount of time.
With over a decade of accumulated data to support its position, the American Dental Association (ADA) has come to the conclusion that teeth whitening products with hydrogen peroxide or carbamide peroxide are safe.