just wanted to add to this as my 3 year old has just had 5 teeth out and still has 2 slightly bad ones at the front. the dentist from the hospital who took her teeth out said it was not only the bottle milk that does it but also breast milk aswell, ( i fed her for quite a long time.) and to stop bedtime bottles all together because the milk basically sticks to the teeth. which is easier said than done i know , but it is not a nice thing to watch your baby being knocked out in a operating room. i know my dd is older but as i found out trying to get a toddler out of a habit is very very hard.
Breast milk is very sweet so not great for teeth. Dental health lady did talk to our bf group and said that it would damage teeth. DD now has 8 teeth at 10.5 months and tbh I don't brush her teeth after her last feed becaus she also falls asleep - but I know I should
I think that the most convincing thing to me is that human babies didn't start getting cavities until we changed our diets and started farming, about 8000 years ago. And there wasn't any option but breastfeeding at the time. I suspect my 12mo DS is far more at risk from the other sugars in other foods than he is from breastmilk.
Back in the here and now... DS 'brushes' his own teeth with a smear of toothpaste and a little toothbrush while I'm changing his nappy just before his last feed (it also keeps his hands out of his nappy - bungo!).