At 50 years old, my teeth are whiter than they were in high school (I have old porcelain crowns from then that are being replaced this week).
I needed to replace the crowns & my dentist recommended whitening prior. 3 15-minute sessions made a dramatic difference! Now, instead of my old crowns being shades whiter than my own teeth, they are now one shade darker!
The only down side is the tender gums for a few days following the procedure. Minimal tooth sensitivity.