It's fine with the boob in it doesn't have the same junk that's in milk that can sit n rot your teeth because boob milk isn't milk in a sense I never took it out of my babies mouth n she has beautiful white teeth but also when her teeth came her pediatrician put coating on them to prevent cavities as well but it's up to you

Some people say it does, some say it doesn't. I wait until they're asleep and pop them off the boob