Final answer:
The outer covering of teeth that protects the tissue underneath is called enamel, the hardest material in the human body, which covers the tooth crown and is susceptible to decay.
Step-by-step explanation:
The tough, white outer covering of teeth that protects the living tissue underneath is called enamel. This protective layer is the hardest material in the human body. It covers the crown of the tooth, which is the part that is visible above the gum line. Beneath the enamel is a layer of dentin, which is a bone-like tissue, extending into the root of the tooth around the innermost part called the pulp cavity. The pulp cavity includes the pulp chamber and pulp canal or root canal, and this area is rich in blood vessels, nerves, and connective tissue. The enamel, despite its hardness, can be susceptible to erosion and tooth decay, commonly in the form of dental caries (cavities), which occur when bacteria in the mouth release acids that degrade enamel.