How far back in history does the toothbrush appear?
Did you ever notice the cavemen on those Geico commercials have all their teeth? It is not because they had toothbrushes; it is due to the fact processed sugar was not invented yet. (They were too busy figuring out why square wheels just can't plow through mammoth dung as easily as they thought).
Hippocrates, the ancient Greek MD and "stand-up philosopher," used a toothpaste made of lizard head and rat parts, rich in tri-calcium phosphate. Yum.
Some folks think the Chinese brought the toothbrush to us; wrong again. Egyptians used a tree bark called "Arak" that was rich in sodium bicarbonate to scrub their teeth.
In the 17th century, a prisoner in London named William Addis drilled small holes in leftover chicken bones from dinner and glued in pieces of string the guards brought him. Upon his release, he entered the retail oral health care business. Plyni the Great dipped his wild boar hair toothbrush into a mix of burnt eggshells and powdered ocean shells, high in calcium carbonate, similar to modern (and tastier!) dentifrices.