It is not only about dental hygiene. I brush my son's teeth twice a day, regulary, since he got his first tooth. He is a very picky eater, does not eat lots of candy.
And yet he is 7 and has 5 fillings. First at the age of 4. His teeth are dense, obviously bad quality, like mine, and nothing helps. My dentist says there is nothing we are doing wrong.
I know a couple of kids that have worse teeth than my son, and go to the dentist every a couple of months. And I know some that have no problem.
I wouldn't blame the Dillards so much