Why are my teeth so sensitive after using Crest 3D White strips(30 minute-once per day) just the 1 time?

It's very common to experience sensitivity from white strips.  The sensitivity should subside within 2 days.  If you are interested in having your teeth whitening, visit your dentist and have them go over teeth whitening options with you.  There are ways to minimize the sensitivity, such as using a fluoridated toothpaste and mouthwash for 2 weeks before your being your whitening procedure.

It is common to have more sensitivty with whitening strips because of their chemical composition. They are much more acidic, so that hey can stay out of the fridge and they are also modified to not flow and be more adherent to the tooth (as they are not designed to be placed in trays). The sensitivity is just the compromise for the convenience. If you so return to conventional tray with or without a chairside session you will find he experience much more relaxing. Kind regardsThomas Dey, BDS, MSc 

Prior to using any whitening product on people with sensitive teeth, I recommend using a highly fluoridated toothpaste for several weeks before whitening. This way, your teeth can build a resistance to the whitening gel. The fluoride is given by prescription, though some dental offices have it as well.