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Glossary

Layers of the teeth

Alternate terms: Cross-section of a tooth; Tissues of the teeth; Tooth layers; What's inside teeth.

Enamel is the hardest substance in the body, and is almost completely mineralized. Dentin has approximately the same hardness as bone, and contains more collagen protein than enamel, making it a bit softer and less wear-resistant. It is porous and permeable, allowing fluid from the pulp to freely move through it.

A cross section of a tooth shows the enamel, dentin, pulp and cementum tissue layers.

Figure 1: The main tissue layers of teeth are illustrated in this cross sectional view. In addition to those shown, cementum comprises the superficial layer of the roots, and serves as the attachment point for fibers of the periodontal ligament, which is a suspensory attachment mechanism that holds teeth into the jaw bones.

Cementum is a tissue to which the fibers of the periodontal ligament attach. The periodontal ligament fibers are elastic, and provide a shock-absorbing suspensory attachment from the tooth to the "alveolar process", an extension of the jaw bones.

Pulp contains blood vessels, nerve tissue, and living cells known as odontoblasts. These are specialized cells that produce dentin throughout the life of the tooth. Other cells reside in the pulp which may perform repair, anti-inflammatory, or immune functions. The cells of the pulp depend on proper circulation of blood through the root apex to remain alive.

If a tooth is injured or extensively decayed, additional blood flows into the tooth, bringing immune cells and nutrients to fight infection and repair the tooth. Unfortunately, the tooth is poorly equipped to deal with increased blood flow, because it can't swell like soft tissue. The result is a toothache, inflamed pulp (pulpitis), and if severe enough, necrosis (death of the vital tissues). This leaves the tooth with a hollow space open to the inside of the body. If bacteria populate the tooth, large infections (abscesses) can result—a common occurrence.

A tooth's crown is the part that you can see in the mouth, protruding from the gingiva (gums). The root is the part that holds the tooth in place in the jaw bone. The apex is the root tip, which has a very small opening (the "apical constriction"), through which nerve and blood vessel tissues of the pulp enter the tooth's root canal.