The girls are all right, it really is up to you!
My girls all had dummies. The twins gave theirs up at 2 1/2 and Lily didn't give hers up until 3 1/2. They only had them for sleep times and for comfort. When Ivy and Noah came along, I just expected that they would use a dummy too. Ivy does. She has it for sleep but unlike the girls she spits it out once she is asleep and Noah never ever took to one, although now he likes to steal Ivy's and wave it in the air!
One out of the three girls looks as though she will need braces. Dave and I both had dummies and my teeth are straight and David needed the works!
I just don't think there is a correlation with the dummy/no dummy/ straight teeth story.
Good luck with your decision!