One of my employees was chomping on ice today when she saw me and said, "I know, I'm not supposed to chew ice! But what's the big deal? Besides, it's crushed ice."
The big deal is that even with crushed ice you could be causing microfractures in your teeth. These are thin cracks that travel from the crown of your molar down to the root. This means that bacteria, and possibly infection, can now pass through your tough enamel and get all the way to the root and nerve of your tooth.
The result is you are susceptible to decay without it being obvious like a cavity. If you were to shine a light from behind your teeth, you would very likely be able to see some of these cracks.
As strong as enamel is, as the hardest bone in your body, your jaws are very powerful, and your teeth aren't for crushing ice, or opening bottles or really anything except eating regular food.
Don't risk needing a root canal down the road, or worse, losing a tooth. Talk to your dentist about this. Chew gum instead. But make sure it's gum with xylitol in it, not sugar or some other non-sugar sweetener. The xylitol is actually good for your teeth. And if you don't have a dentist, time to get one, especially if you're using your teeth as an ice crusher!