The tooth’s outermost layer – the part we brush – is enamel. Deposited by cells called ameloblasts, enamel is 95 percent inorganic, says Gengler, making it the hardest material in the body. In contrast, only about 50 percent of our bone is mineral.

Enamel is thin, though – in dogs and cats, for example, it’s just a fraction of a millimeter in thickness – so most of a tooth’s substance comes from the dentin underneath. Made by cells called odontoblasts, dentin is about 70 percent inorganic and tubular in structure, like a network of “little conduits with liquid inside,” Gengler says.

Inside the tooth, below the dentin, is the pulp chamber. The pulp includes blood vessels that nourish the tooth by delivering oxygen and nutrients, and fast- and slow-conducting nerve fibers that warn us of problems.