Natural Health with Megan Sheppard: Help with teething and glaucoma

You are quite correct, in that breastmilk in itself does not cause cavities. The problem is that once cavities or damage to the enamel appears, the breastmilk may exacerbate the existing issues.
Early childhood caries affects around a tenth of all infants, and the cause is the bacteria Streptococcus mutans. Children diagnosed with early childhood caries tend to have Streptococcus mutans levels that are up to 100 times higher than average. This bacteria can be spread easily by saliva contact, through sharing food, utensils, and cups, and even a kiss.