I looked into your gum whiting questions and was able to find some really good information as noted below.
Chewing gum is not a substitute for brushing well, especially if it contains sugar. Chewing sugar-free gum helps teeth by stimulating saliva. Saliva neutralises acids that can contribute to tooth decay. But many of us salivate enough unaided. It’s good for people who are prone to a dry mouth or don’t produce much saliva.
As for tooth-whitening chewing gum, it won’t change your smile overnight. Tooth-whitening gums contain bicarb soda, also found in tooth-whitening toothpastes.
It’s a good marketing gimmick but the net gain is pretty small and very hard to measure. It won’t make your teeth darker, though.
To maximise the benefits of chewing gum, chew after meals or after eating something sweet, if you can’t find a brush
I hope this has helped