Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Honestly not sure what it did other than cause gum pain.

Used this as directed, and during the application (within the 2 hours), I wasn't experiencing any irritation, but that evening (4-6 hrs after), all my teeth and gums were aching in that unnerving way where you can't do anything to stop it. Sucking air in would create so much sensitivity, drinking liquids..nothing really subsided the sensitivity. Went to sleep finally, and by the next day the nerve pain was gone, but I'm not sure I sensed any whitening results. Probably will avoid these "rapid" whitening kits moving forward :(