The term "tooth" refers to one of the small, hard structures found in the mouths of humans and other animals that are used for biting and chewing food. Teeth are made up of a tough outer layer called enamel, a softer middle layer called dentin, and a inner core of pulp tissue. There are typically 32 teeth in an adult human's mouth, including four types: incisors, canines, premolars, and molars.