Stories by Reidar F. Sognnaes

The status of the problem: Tooth enamel is not a rocklike substance but a living tissue. It is sometimes invaded by bacteria, depending on heredity, nutrition and other factors influencing the individual

It is enamel. Like hair and nails, this hard substance is made by epithelial cells. Once it was thought to be as inert as rock; now it is known to exchange its substance with the body fluids