Tooth Anatomy

Tooth Anatomy

Tooth anatomy is a colloquial term sometimes used to refer to dental anatomy, the field of anatomy concerning the physical structure of teeth. That is a large subject.

Knowledge of the general structure of a human tooth is included in many first-level courses, e.g. in school biology. The following labelled diagram of a 'typical' molar tooth describes basic tooth anatomy in general terms only. (More advanced courses include detailed study of specific types of teeth).

First, what is a molar tooth? There are several types of human teeth. The first set of teeth that develops in young children is temporary, also known as milk teeth. The four types of adult - called permanent teeth are:

  1. Incisors
  2. Canines (also known as cuspids)
  3. Premolars (also known as bicuspids)
  4. Molars

See also teeth names (of human teeth). The parts of the molar tooth labelled in the following simple diagram of tooth anatomy are described in the table below.

Diagram of Tooth Anatomy

Gingiva (Gum)

Note that the diagram above is a simplified representation of a cross-section of a general molar tooth. In reality the relative size and proportions of the parts of the tooth vary from tooth to tooth. Although the lower molars have two roots (as shown above), the upper molars usually have three roots. Purely for ease and clarity of representation in this diagram, blood vessels are shown above in one tooth root and nerves in other other - but in reality all tooth roots contain blood vessels, nerves and lymphatic vessels.

Part of Tooth

Short Description

Main Structure

1.

Crown

The crown of a tooth is the part of the tooth that is above the level of the gums and is covered with enamel.

2.

Neck

The neck of a tooth is the narrowing part of a tooth between the tooth crown and the tooth root.

3.

Root

The root of a tooth consists of one or more projections (two are shown the the diagram above) embedded into the bone. These roots of teeth are embedded into either the mandible (lower-jaw bone) or one of the maxillae (upper-jaw bones), depending on the location in the mouth of the individual tooth.

Detail of Tooth Anatomy

4.

Enamel

Tooth enamel is the hardest substance in the human body. It consists mainly of calcium phosphate and calcium carbonate. Enamel covers the crown of each tooth and is important because its hard structure protects the tooth from mechanical wear e.g. due to chewing food. Tooth enamel also protects the rest of the structure of the tooth from chemical attack by acids that might otherwise dissolve the dentin part of the tooth.

5.

Dentin

The main structure of teeth consists of dentin, which is a calcified connective tissue. This gives the tooth its overall shape and rigidity.

6.

Pulp

Pulp within a tooth is a form of soft connective tissue that includes blood vessels, nerves and lymphatic vessels. It is contained within the central part of the tooth called the "pulp cavity".

7.

Pulp Cavity

The pulp cavity of a tooth is the volume in the centre of the tooth within which is the tooth "pulp" (a connective tissue that contains blood vessels, nerves and lymphatic vessels). The largest part of the pulp cavity is in the centre of the tooth but the pulp cavity also extends down through all of the roots of the tooth. The narrow sections of pulp cavity extending down through the roots of teeth are called "root canals".

8.

Gingivae

Gingivae is the medical term for gums (plural). The singular word for just one "gum" is "gingiva". Gingivae or gums are the oral mucosa covering that that surrounding the base of each tooth forming continuous "gums", one around the upper-jaw and the other around the lower-jaw.

9.

Blood Supply
(to tooth)

Tiny blood vessels supply oxygenated blood to, and drain deoxygenated blood from, each individual tooth. These blood vessels (shown in red and blue in the diagram of tooth anatomy) are part of the human vascular system and pass through the tooth root canals within each of a tooth's roots.

10.

Nerve Supply
(to tooth)

Nerve fibres (examples of which are shown in yellow in the diagram of tooth anatomy) are part of the human nervous system and pass through the tooth root canals within each of a tooth's roots.

11.

Tooth Root Canal

Narrow channels of pulp cavity extend from the main volume of pulp cavity towards the top/center of the tooth along the length of each of the tooth's roots to the apical foramen at the apex of each individual root of the tooth. The tooth root canals contain blood vessels, nerve fibres and lymphatic vessels.

12.

Cementum

Cementum is a calcium-rich layer that covers the root of a tooth. It is light yellow in colour, slightly paler than dentin. Cementum has the highest fluoride content of all mineralized tissue. It is avascular, meaning that the cementum layer itself does not have (or need) blood supply - hence no blood vessels are shown passing through this part of the tooth.

Cementoenamel Junction: The join at which the cementum and enamel coverings of a tooth meet is called the cementoenamel junction, and is also known as the cervical line. In some cases the enamel and cementum do not quite meet, which can result in a sensitive area of tooth, incl. e.g. sensitivity to cold, heat, and/or strong flavours.

13.

Periodontal Ligament

The periodontal ligament lines the sockets in the jaw bones into which teeth are embedded. The periodontal ligament consists of dense fibrous connective tissue that holds each tooth in position within the bone and acts as a mechanical shock absorber when the teeth are subject to various mechanical forces during use to chew food.

14.

Apical Foramen

An apical foramen is the opening at the root of a tooth through which nerves, lymphatic vessels and blood vessels enter the pulp cavity of the tooth. Each tooth has as many apical foramen as it has roots, so one, two or three - depending on the type of human tooth.

15.

Alveolar Bone

Alveolar bone is sometimes labelled alveolar process and is the thick ridge part of the jaw bones, i.e. the mandible (lower-jaw bone) or maxillae (upper-jaw bones), in which the tooth sockets are located.

The mineral content of alveolar bone includes hydroxyapatite, which is also found in tooth enamel. Alveolar bone includes an area of compact bone called lamina dura to which the cementum covering the roots of teeth is attached by the periodontal ligament.

See also structures of the mouth and teeth names.

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