I work at a dental product research company and we have received several offers from companies like this to test their products. They are completely serious and it is 100% legal for parents to to this to their kids and on themselves.
It's just ridiculous that they could expect the average joe to understand the full anatomy and physiology of a tooth to a point that they could properly excavate caries without either doing to much or simply filling over decay that they didn't remove in the first place