The Anatomy of a Tooth: Enamel, Dentin, Pulp, and Root

A tooth looks like a simple white lump, but it is really a set of layers, each made of a different material and each with its own job. Knowing what those layers are makes almost everything else about dental health easier to follow, from why a cavity hurts at a certain depth to why a loose tooth is a warning sign. This is a plain tour from the outside in.

Two halves: crown and root

Every tooth has two main regions. The crown is the part you can see above the gum. The root is the part hidden below the gumline, set into a socket in the jawbone. A rough rule is that the root is often as long as, or longer than, the crown, so most of a tooth is out of sight. The narrow zone where crown meets root, right at the gumline, is called the neck, and it is a spot that needs attention because plaque likes to gather there. Wrapping around the neck of each tooth is the gum, or gingiva, which forms a tight collar over the join between crown and root and helps keep bacteria out of the space below.

Enamel: the armor

The outer shell of the crown is enamel, and it is the hardest tissue the human body produces. Enamel is almost entirely mineral, which is what makes it so tough and lets it handle a lifetime of biting and chewing. It has no nerves and no blood supply of its own. Enamel is also slightly translucent, so much of a tooth's color actually comes from the dentin beneath it showing through. That is why teeth are naturally shades of off-white and ivory rather than pure white.

That last fact has a big consequence. Because enamel contains no living cells, it cannot grow back or heal a hole the way skin heals a cut. Its surface can take minerals back in and harden slightly, the repair process behind how early decay can stall or reverse, but once enamel actually breaks, the body cannot rebuild it. That is why a dentist has to fill a cavity rather than wait for it to mend.

Dentin: the bulk of the tooth

Under the enamel is dentin, a slightly softer, yellowish tissue that makes up most of the tooth. Dentin is not solid. Under a microscope it is threaded with thousands of tiny tubes that run from the outer layer inward toward the tooth's core. Those tubes are filled with fluid and connect to nerve endings.

This structure explains a common experience. When enamel wears thin or a filling is deep, hot, cold, or sweet things can trigger a short, sharp twinge. The stimulus travels along the fluid in those tubes and reaches the nerve. Dentin is also a living tissue, and unlike enamel it can slowly lay down more of itself over the years, thickening in response to wear or irritation.

Pulp: the living core

At the center of the tooth is the pulp, a soft chamber of nerves, blood vessels, and connective tissue. The pulp is the tooth's supply line. It brings nourishment while the tooth is forming and carries the nerves that let a tooth sense pressure and temperature.

When people talk about a serious toothache, the pulp is usually involved. If decay or a crack reaches this chamber, the tissue inside can become inflamed and swollen. Because the pulp sits in a hard, sealed space, that swelling has nowhere to expand, which is part of why deep dental pain can be so intense. Understanding this path, from surface enamel down to the pulp, is really the story of how a cavity gets worse when it is left alone.

Root, cementum, and the anchor

The root is what holds a tooth in place, and it has its own set of parts.

• Cementum is a thin, bone-like layer that covers the outside of the root. It is softer than enamel and gives the anchoring fibers something to grip.
• The periodontal ligament is a cushion of tiny fibers that connect the cementum to the surrounding jawbone. It holds the tooth firmly yet lets it flex a fraction under a bite, acting like a shock absorber.
• The alveolar bone is the part of the jaw that forms the socket and grips the root.

Running up the middle of each root is a narrow channel, the root canal, which carries the nerves and vessels of the pulp out through a small opening at the tip. A tooth can have one root or several, depending on where it sits in the mouth.

A tooth is not just the white part you brush. It is a living organ held in the jaw by a network of soft tissue and bone, and most of it lives below the gumline.

Why the supporting cast matters

It is tempting to think of dental health as being only about the enamel you can see. But the ligament and bone that hold a tooth are just as important, and they are exactly what is lost in advanced gum disease. A perfectly healthy crown is no use if the foundation under it fails.

The same layered design appears in children's teeth, though on a smaller scale and with thinner enamel, which is one reason a child's first teeth need real care even though they are temporary. For clear overviews of tooth structure aimed at the general public, the American Dental Association's consumer information is a reliable place to start at ada.org.

This guide is educational and general. Teeth vary from person to person, and only a dentist examining your own mouth can tell you about the specific tooth you are wondering about.