The light on your teeth is ok for the first 2 treatments. It feels like toothpaste that's a little to hot. When it was time for the 3rd treatment there 15 minutes apart. The lady at the dentist did say some pain once the 3rd treatment. Well was fine until 9 mins in the 3rd procedure. The pain I feel now and felt was like a live nerve jumping out of your mouth. I literally have to hold my mouth for dear life to hope the pain stops.I couldnt evern get the 4th treatment, I was in too much pain. Cant imagine if I stayed to have all of the treatments done. the pain would only have gotten worse. I told the office they would of had to take me to the er. It's like a bad toothache jumping all over your mouth in spurts. you dont even get a warning when its coming it just come.. NOt worth it to much pain.