Is it normal for teeth to have white spots after whitening?

After whitening your teeth with the Philips Sonicare Teeth Whitening Pen, you may notice whiter spots on your teeth. This can be caused by temporary dehydration of the teeth.

Any uneven whitening will fade 2-7 days after using the whitening pen, with the final result being visible around 1 week after use. The area of the tooth closest to the gum may take longer to whiten than the biting edge.