A tooth is a hard, bony structure found in the jaws or mouth of vertebrates, used for grasping and chewing food, as well as for defense. Each tooth has a crown, which is the visible part above the gum, and one or more roots that anchor it in the jawbone. The tooth's structure consists of three layers: enamel, the hardest tissue in the body, covering the crown; dentin, which forms the bulk of the tooth; and pulp, the innermost part containing nerves and blood vessels. Humans typically have two sets of teeth: 20 primary (deciduous) teeth and 32 permanent teeth.

What are the main parts of a tooth?

A tooth is composed of three main layers: enamel, dentin, and pulp. Enamel is the hardest tissue in the body, covering the crown of the tooth. It is inorganic and contains no nerves. Dentin makes up the bulk of the tooth, lying beneath the enamel. It is harder than bone but softer than enamel. Pulp is the innermost part of the tooth, containing nerves, blood vessels, and connective tissue. It nourishes the dentin. The root of the tooth, which is below the gumline, is covered by cementum, a bone-like tissue that anchors the tooth.

What is the function of enamel on a tooth?

Enamel is the hardest tissue in the human body and covers the crown of a tooth . It is primarily composed of apatite crystals, containing calcium and phosphate. Mature enamel is not living and has no nerves. Its primary function is to protect the underlying dentin and pulp from wear and decay. The enamel's hardness varies, being densest at the biting edges. It is also highly resistant to caries (tooth decay) due to its surface properties and fluoride content. Malformations like hypoplasia (insufficient enamel matrix) or hypocalcification (insufficient calcium) can lead to softer enamel.

What is the role of dentin in tooth structure?

Dentin is the yellowish tissue that forms the bulk of a tooth's structure. It is harder than bone but softer than enamel. Dentin is primarily composed of apatite crystals, which are made of calcium and phosphate. In humans and other mammals, specialized cells called odontoblasts line the tooth's pulp cavity. These cells extend into the dentin through tubules, and these extensions are responsible for transmitting sensations of pain, pressure, and temperature to the nerve in the pulp chamber. Throughout life, secondary dentin is produced as a repair material, particularly in areas affected by cavities or wear.

What is the pulp, and why is it important?

The pulp is the soft tissue found in the center of a tooth, containing nerves, blood vessels, and connective tissue. It is crucial for tooth health as it nourishes the tooth and transmits sensations like pain, pressure, and temperature. The importance of the pulp lies in its role in maintaining the vitality of the tooth. When the pulp becomes diseased or damaged, often due to decay or injury, it can lead to infection. Procedures like root canal therapy involve removing the diseased pulp to save the tooth and prevent further complications. Preserving the natural tooth, even after pulp removal, is vital for maintaining the dental arch and offers superior function compared to artificial teeth.

How do the different types of teeth (incisors, canines, molars) vary in structure and function?

In human anatomy, teeth are specialized for different functions. Incisors, located at the front of the mouth, are adapted for cutting and biting food. Canines, situated next to the incisors, are typically pointed and used for tearing food. Molars and premolars, found at the back of the mouth, have broader, flatter surfaces with cusps designed for grinding and crushing food. The structure of each tooth type reflects its function. Incisors have sharp edges for slicing. Canines are often the longest teeth and have a single cusp for piercing and tearing. Molars and premolars possess multiple cusps and a larger surface area to facilitate efficient grinding. Humans, as omnivores, have a combination of these tooth types, allowing for a varied diet.

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Images, Videos & Interactives

A labeled cross section illustration of an adult human molar shows the tooth's crown and root, with layers including enamel, dentin, and pulp, as well as gum, cementum, blood vessels, periodontal ligament, lateral canals, and nerve.

Teeth in vertebrates have been adapted for special uses

The video thumbnail image shows a brown-speckled bird perched on a branch, singing with an open beak.

A dentist holds a glass of water while a child with an exaggerated smile reclines in a dental chair. The water glass is circled, and arrows point to it.

A person holds a piranha from the Napo River in Ecuador, showing its sharp, triangular teeth and red-orange lower jaw as they remove a fishing hook from its mouth.

tooth size comparison: megalodon and modern great white shark

At a Glance

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Also known as: teeth

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Top Questions

What is a tooth?
A tooth is a hard, bony structure found in the jaws or mouth of vertebrates, used for grasping and chewing food, as well as for defense. Each tooth has a crown, which is the visible part above the gum, and one or more roots that anchor it in the jawbone. The tooth's structure consists of three layers: enamel, the hardest tissue in the body, covering the crown; dentin, which forms the bulk of the tooth; and pulp, the innermost part containing nerves and blood vessels. Humans typically have two sets of teeth: 20 primary (deciduous) teeth and 32 permanent teeth.
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What are the main parts of a tooth?
A tooth is composed of three main layers: enamel, dentin, and pulp.
- Enamel is the hardest tissue in the body, covering the crown of the tooth. It is inorganic and contains no nerves.
- Dentin makes up the bulk of the tooth, lying beneath the enamel. It is harder than bone but softer than enamel.
- Pulp is the innermost part of the tooth, containing nerves, blood vessels, and connective tissue. It nourishes the dentin.
The root of the tooth, which is below the gumline, is covered by cementum, a bone-like tissue that anchors the tooth.
7 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What is the function of enamel on a tooth?
Enamel is the hardest tissue in the human body and covers the crown of a tooth. It is primarily composed of apatite crystals, containing calcium and phosphate. Mature enamel is not living and has no nerves. Its primary function is to protect the underlying dentin and pulp from wear and decay. The enamel's hardness varies, being densest at the biting edges. It is also highly resistant to caries (tooth decay) due to its surface properties and fluoride content. Malformations like hypoplasia (insufficient enamel matrix) or hypocalcification (insufficient calcium) can lead to softer enamel.
2 Britannica Sources
1. enamel
2. dentin
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What is the role of dentin in tooth structure?
Dentin is the yellowish tissue that forms the bulk of a tooth's structure. It is harder than bone but softer than enamel. Dentin is primarily composed of apatite crystals, which are made of calcium and phosphate.

In humans and other mammals, specialized cells called odontoblasts line the tooth's pulp cavity. These cells extend into the dentin through tubules, and these extensions are responsible for transmitting sensations of pain, pressure, and temperature to the nerve in the pulp chamber. Throughout life, secondary dentin is produced as a repair material, particularly in areas affected by cavities or wear.
2 Britannica Sources
1. enamel
2. dentin
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What is the pulp, and why is it important?
The pulp is the soft tissue found in the center of a tooth, containing nerves, blood vessels, and connective tissue. It is crucial for tooth health as it nourishes the tooth and transmits sensations like pain, pressure, and temperature.

The importance of the pulp lies in its role in maintaining the vitality of the tooth. When the pulp becomes diseased or damaged, often due to decay or injury, it can lead to infection. Procedures like root canal therapy involve removing the diseased pulp to save the tooth and prevent further complications. Preserving the natural tooth, even after pulp removal, is vital for maintaining the dental arch and offers superior function compared to artificial teeth.
3 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How do the different types of teeth (incisors, canines, molars) vary in structure and function?
In human anatomy, teeth are specialized for different functions. Incisors, located at the front of the mouth, are adapted for cutting and biting food. Canines, situated next to the incisors, are typically pointed and used for tearing food. Molars and premolars, found at the back of the mouth, have broader, flatter surfaces with cusps designed for grinding and crushing food.

The structure of each tooth type reflects its function. Incisors have sharp edges for slicing. Canines are often the longest teeth and have a single cusp for piercing and tearing. Molars and premolars possess multiple cusps and a larger surface area to facilitate efficient grinding. Humans, as omnivores, have a combination of these tooth types, allowing for a varied diet.
6 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

tooth, any of the hard, resistant structures occurring on the jaws and in or around the mouth and pharynx areas of vertebrates. Teeth are used for catching and masticating food, for defense, and for other specialized purposes.

The teeth of vertebrates represent the modified descendants of bony dermal (skin) plates that armored ancestral fishes. A tooth consists of a crown and one or more roots. The crown is the functional part that is visible above the gum. The root is the unseen portion that supports and fastens the tooth in the jawbone. The root is attached to the tooth-bearing bone—the alveolar processes—of the jaws by a fibrous ligament called the periodontal ligament or membrane. The “neck” of the root is embraced by the fleshy gum tissue (a specialized area of connective tissue covered with mucous membrane that lines the mouth cavity). The shape of the crown and root vary among different teeth and among different species of animals.

The structure of teeth

All true teeth have the same general structure and consist of three layers. In mammals an outer layer of enamel, which is wholly inorganic and is the hardest tissue in the body, covers part or all of the crown of the tooth. The middle layer of the tooth is composed of dentine, which is less hard than enamel and similar in composition to bone. The dentine forms the main bulk, or core, of each tooth and extends almost the entire length of the tooth, being covered by enamel on the crown portion and by cementum on the roots. Dentine is nourished by the pulp, which is the innermost portion of the tooth. The pulp consists of cells, tiny blood vessels, and a nerve and occupies a cavity located in the center of the tooth. The pulp canal is long and narrow with an enlargement, called the pulp chamber, in the coronal end. The pulp canal extends almost the whole length of the tooth and communicates with the body’s general nutritional and nervous systems through the apical foramina (holes) at the end of the roots.

Below the gumline extends the root of the tooth, which is covered at least partially by cementum. The latter is similar in structure to bone but is less hard than dentine. Cementum affords a thin covering to the root and serves as a medium for attachment of the fibers that hold the tooth to the surrounding tissue (periodontal membrane). Gum is attached to the adjacent alveolar bone and to the cementum of each tooth by fiber bundles.

Tooth form and function

Like most other mammals, humans have two successive sets of teeth during life. The first set of teeth are called primary, or deciduous, ones, and the second set are called permanent ones. Humans have 20 primary and 32 permanent teeth.

Primary teeth differ from permanent teeth in being smaller, having more pointed cusps, being whiter and more prone to wear, and having relatively large pulp chambers and small, delicate roots. The primary teeth begin to appear about six months after birth, and the primary dentition is complete by age 2 1/2; shedding begins about age 5 or 6 and is finished by age 13. The primary teeth are shed when their roots are resorbed as the permanent teeth push toward the mouth cavity in the course of their growth.

In humans the primary dentition consists of 20 teeth— four incisors, two canines, and four molars in each jaw. The primary molars are replaced in the adult dentition by the premolars, or bicuspid teeth. The 12 adult molars of the permanent dentition erupt (emerge from the gums) behind the primary teeth and do not replace any of these, giving a total of 32 teeth in the permanent dentition. The permanent dentition is thus made up of four incisors, two canines, four premolars, and six molars in each jaw.

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Incisor teeth are the teeth at the front of the mouth, and they are adapted for plucking, cutting, tearing, and holding. The biting portion of an incisor is wide and thin, making a chisel-shaped cutting edge. The upper incisors have a delicate tactile sense that enables them to be used for identifying objects in the mouth by nibbling. Next to the incisors on each side is a canine, or cuspid tooth. It frequently is pointed and rather peglike in shape and, like the incisors, has the function of cutting and tearing food.

Premolars and molars have a series of elevations, or cusps, that are used for breaking up particles of food. Behind each canine are two premolars, which can both cut and grind food. Each premolar has two cusps (hence the name bicuspid). The molars, by contrast, are used exclusively for crushing and grinding. They are the teeth farthest back in the mouth. Each molar typically has four or five cusps. The third molar in humans tends to be variable in size, number of roots, cusp pattern, and eruption. The number of roots for each type of tooth varies from one for incisors, canines, and premolars to two or three for molars.

Teeth in other animals

The teeth of many vertebrates have been adapted for special uses. Rodents have curved incisors that are set deep in the jaws and which grow continually throughout life; hares and rabbits have similar teeth. The tusks of elephants are enlarged upper incisors. The tusks of the walrus are enlarged canines, as are those of the wild boar. In the pig the lower incisors lie close together and project forward to form a digging instrument. Baboons have enlarged canines for defense and display. Certain snakes have hollow teeth that function as needles to insert venom. The sawfish, the only animal with true teeth outside its mouth, uses the teeth on both sides of its snout to slash its prey. The forms, patterns, and arrangements of teeth in different species of animals are of great importance in determining their phylogenetic (taxonomic) relationships.

tooth

The structure of teeth

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Tooth form and function

Teeth in other animals