A good system doesn't come cheap. Cheap options are better to avoid, I once bought one, it was my very first one, and after a month I threw it away. Then I switched to a more expensive one, which I can charge from any wire. If you use one of those, you have to wash it and brush your teeth before you use it. You can apply an extra gel, but UV whitening without gel is the safest. Insert and hold for 15 minutes, or as long as your teeth can withstand, as the mouthpiece heats up. My Implant dentist in Eastlake OH who I visit every year, is skeptical of such devices, he thinks they make the teeth sensitive. This may be true.