I used the 3D whiten strip last night and left it on for an hour. They hurt bad. What should I do?

You can use toothpaste specifically for sensitive teeth, such as sensodyne.  I also recommend getting a fluoride rinse.  Fluoride helps with tooth sensitivity by blocking the channels with which the fluid in your teeth travel.  You can also take some ibuprofen to help with the discomfort.  The good news is that sensitivity should not last more than 48 hours.

Hi Amanda,I agree with Dr. Mahooti's recommendation of using sensodyne. I, myself, have very sensitive teeth- the sensodyne helps quite a bit. Use it as your everyday toothpaste (2x a day) when you're bleaching, and don't rinse out your mouth- just spit the toothpaste out. This will increase its effectiveness, as the potassium nitrate in the toothpaste will have more time to penetrate into the teeth. For immediate help, you can also take ibuprofen (advil/motrin) if you have no allergies or contraindications.Additionally, for the future, make sure you note the duration of time the strip should be left in the mouth (some are only recommended for 15 minutes, whereas others are recommended for up to 6-8 hours depending on the bleaching agent used)... If you know you have severe sensitivity when using whitening products, only use them for half of the recommended time and see if that helps. Over-the-counter white strips can be quite harsh, as they usually do not have any desensitizing agents in them. If you are looking for great results with minimal sensitivity, I would suggest asking your dentist about in-office whitening options, as they more often than not have desensitizing agents in them and give much better results in much less time. Lastly, if you are doing at-home whitening, make sure you don't get any of the bleaching solution on your gums, as this can cause bleach burns, gum sensitivity, and gum discoloration. 

Sensitivity after whitening is common and can take 3-4 days to subside. Until then, you can help aid the pain by taking ibuprofen. If the pain persists after the usual 3-4 day period, contact your dentist...your teeth may be sensitive due to an issue that needs professional attention.See the provided link for info about whitening methods for sensitive teeth. This may be a good to keep in mind for future whitening. 

For tooth  sensitivity after  whitening, you can use Sensodyne toothpaste. You can dab it on your fingers and apply to the sensitive teeth. Don't rinse it off right away. You can do this at night for about a week or so too. If you feel discomfort or burning on your gums, you can open up a vitamin E capsule and apply the oil on the gums. If the sensitivity lingers and you are still uncomfortable, you should see a dentist.