I had this done and it was more like 300, not 600. I experienced the "dehydrated" white look and the dentist and his assistants were all "excited" about my improvement. But, yes, an hour or 2 later, they were not as white as when everyone was raving about the improvement. I never experienced heat sensitivity, but while in the chair, it was actually rather unpleasant. I had what they called "zingers" that felt like sharp pains going through my teeth... they were the tooth equivalent of getting accidentally zapped on the arm. They did not feel good AT ALL. In the end, I wouldn't do it again for any price. The results were mediocre; the pain was not worth it.