Update 1 Year Later: https://youtu.be/odQNs29Lc_U
(are the teeth yellow again?)
I have stained yellow teeth. Was recommended crest 3d white strips by a friend and after a year of it sitting in my drawer I decided to use them for 20 days.
I only used the strips on my upper teeth and left the bottom untreated for your entertainment.
No gum/teeth sensitivity was felt during the entire 20 days of use.