Laser teeth whitening is normally done in three 20-minute bleaching treatments. With laser teeth whitening treatments you are able to walk out of the dental office with your teeth a lot brighter. With laser bleaching, a barrier is put around the gums and a strong bleach is put on your teeth. A laser light is used to activate the bleach to make it work. A down side of laser teeth whitening treatments can be the cost since laser whitening is the most expensive of the teeth-whitening options available.