I don't think its the milk as such, but more the teat on the bottle that can cause their teeth to move forward. I wouldn't worry though. My SIL was still giving her DD a bottle at around 18 months and the MCHN had a fit - but SIL's sister works for a dentist and didn't say anything about it. I figured if it was such an issue, then her sister would've certainly said something.

FWIW - DD has her nighttime milk in a sippy cup, we still have cuddles and it didn't make a difference at all.