Instruct: Classify Amazon reviews into positive or negative sentiment
Query: DO NOT PURCHASE

Although I am satisfied with the brightening of my teeth, my lower gums still have severe tenderness and soreness a full three days after the treatment. I was only able to get through three of the four sessions becuse of the tenderness on my gums. I have used other whitening systems in the past without any issues, so I was suprised at my experience.I will not use the rest of this product or purchase it again in the future because of the way my teeth and gums have reacted. I advise trying another whitening product.