The LED teeth whitening light will not make your teeth whiter however it will accelerate the teeth whitening gel, thus causing it to react quicker when breaking down tough to fight stains. If you do not have custom fitted bleaching trays that are created using an exact mold of your teeth then you would benefit from using an LED tooth whitening light during treatment's to reduce the time of having the gel exposed in your mouth.
It is not mandatory to leave the light in your mouth for the full 45-120 minute treatment but 20-40 minutes with the light is advised.
Available at home teeth whitening systems in order of most to least effective:
Custom Teeth Whitening (bleaching) Trays: once you have ordered the bleaching tray creation kit you use the materials provided and take your upper and lower dental impressions - mail them back to the dental lab from which they use the impression to create a set of teeth whitening trays specific to your teeth - mail them back to you for you to begin your whitening treatment's. The custom trays are optimal because they fit your teeth with precision.
LED Teeth Whitening Light With Gel Pen: using the brush tip applicator apply the teeth whitening gel on the front surface of your front teeth - insert the lip protector tray - insert the LED light and go! Be sure to use carbamide peroxide sticky formula gel such as that sold by smilebrilliant.com to ensure the gel holds to your teeth during treatment.
Teeth Whitening Strips: while they are effective to a degree they can be a hassle to keep on your teeth without slippage. In addition it is common to achieve splotchy results considering there is a very thin layer of hydrogen peroxide on the strip which can scrunch leaving inconsistent coloring of the teeth. Given the average cost to whitening strips seems to range between $50-$100; it is in your best interest to purchase custom fitted bleaching trays from an online retailer such as smilebrilliant.com for around $89.95. You could also purchase an LED light to accelerate the whitening gel during treatment.