Many parents are unsure of when their children need to first see the dentist. The easy answer is "First visit by first birthday." That's the opinion of the American Academy of Pediatric Dentistry. The American Academy of Pediatrics indicates that children who are at risk of early childhood cavities need to see a pediatric dentist by age 1. This idea of such early dental visits is still surprising to many adults, but national research has revealed that the incidence of cavities have been increasing in preschool-aged children. More than 25% of children in the United States has had at least one cavity by the age of 4, but many kids get cavities as early as age 2.

You should take the children to the dentist at 6 months / when they get their first 2 teeth. Those teeth will be the only teeth she has until her pre teen years. Don't wait for half of her mouth to fill up before you get them cleaned. Plus it is very educational for the parents to learn how and techniques to use that are helping. Some people who brush the infants teeth aren't actually doing a good job. Plaque forms on a tooth as soon as it sprouts. From germs food bacteria formula etc.