I need to know about 'Extra' ICE Chewing Gum...?

I bought a packet of it because it looked really minty (I love STRONG mints) yesterday. I was reading the front of the packet and it says "with Microgranules" and a picture of a tooth. What are these 'microgranules' and what do they do? My mates say they whiten your teeth? Did I just buy a toothwhitening for 40 p?