From whether to use manual or electric and how much fluoride your toothpaste should contain.
All of us have seen lots of them, those words of warning or instruction that appear on products we buy. "Do not eat this sled." "For best results do not apply this floor wax to your teeth." "This antifreeze is not intended for pouring on breakfast cereal." We hardly notice them, let alone consider what they say about the times in which we live.