I have pretty good natural teeth [SEP] I have pretty good natural teeth, who just have become less white and lusterous as I age and have periodically drank coffee. After only 1 treatment I can see a difference. I have always had good teeth and this has just boosted the natural health and brilliance of my teeth. I think people just need to be realistic on expectations, this device is not going to correct permanent damage that has occurred, it is just gonna whiten and it has, after one treatment I noticed a difference.