I read reviews on the procedure and got super nervous about the pain from the zingers and blisters that happened to some people on their gums. I still went through with the whitening and made sure the dentist coated my gums well for protection. I felt the zingers on the second light treatment( They usually do the light treatment four times in one visit). The zingers weren't too bad at first but did hurt more but the third. He asked if I wanted to do a fourth... I said no because I was scared the pain would be too bad like in the reviews. When I got home the pain did get a lot worse, but I drank some white wine and that helped a bit. When I woke up the next day... no more zingers no pain at all and no sensitivity. I would do the procedure again, my teeth are a lot whiter... but I wish I had done the fourth to get them even brighter. There are some cons... Some areas on the teeth are spotty white but only noticeable close up. Also, my front tooth was bonded before this for a largely chipped tooth. My dentist tried to match it to the new color but it still looks a little more yellow that the rest... I may have a veneer put on in the near future to match better. I would do it again and not be so nervous next time!