The rule of thumb is that your baby should visit the dentist immediately after the eruption of the first tooth. (babygearspecialist.com)
When kids are breastfeeding exclusively, again there are those protective parts of the breast milk that help to protect the teeth, it's kind of after the introduction of the bacteria, sometime around the time of the eruption of the first tooth, somewhere around there, so 4 - 6 months. (pregnancymagazine.com)
Really focusing on their own oral hygiene is really important, because once babies are born, from that time to about the time of the eruption of the first tooth, which happens around 6 months of age for babies, some babies as early as 4 months, some as late as a year, they actually get colonized with strep mutans, which is a particular bacteria that causes cavities. (pregnancymagazine.com)