Yes, to both. (assuming by "chipped" you don't mean a chip the size of a raisin.) I actually see this every day. I'm a teeth grinder (bruxism), currently without a nightguard. Every morning I look in the mirror to see how far down I ground my four front teeth, especially the 2 upper big ones. (I'm a mild grinder--it's never more than 1 mm, maybe 1+1/2.) But as the day goes on they grow in. By the time it's bedtime they're almost back to normal, and if I use a nightguard for 3 or 4 nights straight, they're perfect.