I said I wouldn't use them either, but I did! For comfort sucking, as a PP has already mentioned.

I was very strict with DS' dummy usage, only allowing him to have it when he was very unsettled and never let him go to sleep with it, so he was spitting it out of his own accord by the time he was 3 months old. He was fully breastfed and as the first child I had plenty of time to give him a comfort breastfeed. His teeth are perfect.

DD on the other hand was on formula full time by the age of 3 months (another story) and needed more sucking time, as a bottle feed is over much quicker than a breastfeed, so she was allowed the dummy far more. And I didn't have as much time to settle her to sleep because I had a toddler so we allowed her to use the dummy to get herself off to sleep.

However when she was 12 months she had her first dentist appointment - only because DS was having his and they offered to check DD as well. The dentist was actually a paediatric dentist and she took one look at DD's teeth and said "well I can see she uses a dummy." I was most taken aback because DD didn't have it in her mouth all the time (we wouldn't allow that) and would spit it out once she was asleep. But the dentist showed me that the dummy was actually preventing her 2 top teeth from growing down properly and said that if we got rid of it asap that should be rectified. However, she couldn't say for sure if it would have already affected the way her adult teeth will grow in.

So we ditched it straight away and within 2 weeks DD's front teeth had grown down more.

The dentist explained that the sucking on the dummy changes the muscle forces in the jaw, which then changes the way the jaw grows and then the teeth grow in crooked.

That said, I was a finger sucker and my siblings were dummy suckers and my teeth were by far the worst. So I would encourage dummy use over thumb sucking but then get rid of the dummy as soon as possible.

It does seem to be a bit "luck of the draw" and dummy or thumb sucking seems to affect the teeth of some kids more than others.