Craze line or crack? Does that mean they are cracks and Invisalign could make them worse? (photo)

Many years ago a dental hygienist asked if I had pain in a tooth because she saw a crack. Don't know which tooth she meant, but that has never been brought up by any other dentist or ortho. Now I'm about to start Invisalign and heard about people cracking teeth during treatment. I have 2 lines I thought were "craze lines" on my front teeth but I can actually feel them when I run over then with a dental pick.