Are you only an occasional gum chewer? If so, and you figure it can't hurt to pick up a pack of "whitening" gum, you should know that your teeth won't get any whiter unless you're constantly chewing the stuff.
you have to chew so much whitening gum for it to work pic.twitter.com/2to4qY8ze5
— Steve Luvender (@steveluvender) August 30, 2017
Take a look at that label -- you'd need to spend a full hour of every day chewing this gum, just to notice a difference after three months.
Orbit doesn't link to the study anywhere I can find, so we don't even know how much of a difference those 84 hours of gum-chewing made. Did people's teeth go from yellow to ever-so-slightly less yellow? Or was it the kind of change you can easily see in the mirror? Looks like you'll have to chew 420 pieces of gum to find out.