Tooth
Overview
Teeth are small, calcified
Calcification
Calcification is the process in which calcium salts build up in soft tissue, causing it to harden. Calcifications may be classified on whether there is mineral balance or not, and the location of the calcification.-Causes:...

, whitish structures found in the jaw
Jaw
The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of...

s (or mouth
Mouth
The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....

s) of many vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

s that are used to break down food
Food
Food is any substance consumed to provide nutritional support for the body. It is usually of plant or animal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals...

. Some animals, particularly carnivore
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...

s, also use teeth for hunting or for defensive purposes. The roots of teeth are embedded in the Mandible bone or the Maxillary bone and are covered by gums
Gingiva
The gingiva , or gums, consists of the mucosal tissue that lies over the mandible and maxilla inside the mouth.-General description:...

. Teeth are made of multiple tissues of varying density and hardness.

Teeth are among the most distinctive (and long-lasting) features of mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

 species.
Encyclopedia
Teeth are small, calcified
Calcification
Calcification is the process in which calcium salts build up in soft tissue, causing it to harden. Calcifications may be classified on whether there is mineral balance or not, and the location of the calcification.-Causes:...

, whitish structures found in the jaw
Jaw
The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of...

s (or mouth
Mouth
The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....

s) of many vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

s that are used to break down food
Food
Food is any substance consumed to provide nutritional support for the body. It is usually of plant or animal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals...

. Some animals, particularly carnivore
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...

s, also use teeth for hunting or for defensive purposes. The roots of teeth are embedded in the Mandible bone or the Maxillary bone and are covered by gums
Gingiva
The gingiva , or gums, consists of the mucosal tissue that lies over the mandible and maxilla inside the mouth.-General description:...

. Teeth are made of multiple tissues of varying density and hardness.

Teeth are among the most distinctive (and long-lasting) features of mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

 species. Paleontologists
Paleontology
Paleontology "old, ancient", ὄν, ὀντ- "being, creature", and λόγος "speech, thought") is the study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments...

 use teeth to identify fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

 species and determine their relationships. The shape of an animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

's teeth is related to its diet. For example, plant matter is hard to digest, so herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...

s have many molars
Molar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....

 for chewing
Mastication
Mastication or chewing is the process by which food is crushed and ground by teeth. It is the first step of digestion and it increases the surface area of foods to allow more efficient break down by enzymes. During the mastication process, the food is positioned between the teeth for grinding by...

 and grinding. Carnivore
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...

s, on the other hand, need canines to kill prey and to tear meat.

Mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s are diphyodont
Diphyodont
A Diphyodont is an animal with two successive sets of teeth, first the "deciduous" set and later the "permanent" set. Most mammals are Diphyodonts. Diphyodonts contrast with Polyphyodonts, such as many fish, whose teeth are constantly replaced....

, meaning that they develop two sets of teeth. In human
Human
Humans are the only living species in the Homo genus...

s, the first set (also called the "baby", "milk", "primary", and "deciduous
Deciduous teeth
Deciduous teeth, otherwise known as reborner teeth, baby teeth, temporary teeth and primary teeth, are the first set of teeth in the growth development of humans and many other mammals. In some Asian countries they are referred to as fall teeth as they will eventually fall out, while in almost all...

" set) normally starts to appear at about six months of age, although some babies are born with one or more visible teeth, known as neonatal teeth
Neonatal teeth
Natal teeth are teeth that are present at birth.Neonatal teeth are teeth that emerge through the gingiva during the first month of life.The incidence of neonatal teeth varies considerably, between 1:700 - 1:30,000 depending on the type of study...

. Normal tooth eruption
Tooth eruption
Tooth eruption is a process in tooth development in which the teeth enter the mouth and become visible. It is currently believed that the periodontal ligaments play an important role in tooth eruption...

 at about six months is known as teething
Teething
Teething is the process by which an infant's first teeth sequentially appear by emerging through the gums. Teething may start as early as three months or as late, in some cases, as twelve months. The typical time frame for the first teeth to appear is somewhere between six and nine months...

 and can be painful.

Some animals develop only one set of teeth (monophyodont) while others develop many sets (polyphyodont). Shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....

s, for example, grow a new set of teeth every two weeks to replace worn teeth. Rodent
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....

 incisors grow and wear away continually through gnawing, which helps maintain relatively constant length. The industry of the beaver
Beaver
The beaver is a primarily nocturnal, large, semi-aquatic rodent. Castor includes two extant species, North American Beaver and Eurasian Beaver . Beavers are known for building dams, canals, and lodges . They are the second-largest rodent in the world...

 is due in part to this qualification. Many rodents such as vole
Vole
A vole is a small rodent resembling a mouse but with a stouter body, a shorter hairy tail, a slightly rounder head, smaller ears and eyes, and differently formed molars . There are approximately 155 species of voles. They are sometimes known as meadow mice or field mice in North America...

s (but not mice
MICE
-Fiction:*Mice , alien species in The Hitchhiker's Guide to the Galaxy*The Mice -Acronyms:* "Meetings, Incentives, Conferencing, Exhibitions", facilities terminology for events...

) and guinea pig
Guinea pig
The guinea pig , also called the cavy, is a species of rodent belonging to the family Caviidae and the genus Cavia. Despite their common name, these animals are not in the pig family, nor are they from Guinea...

s, as well as rabbit
Rabbit
Rabbits are small mammals in the family Leporidae of the order Lagomorpha, found in several parts of the world...

s, have continuously growing molars in addition to incisors.

Dental trauma refers to trauma to the face, mouth, and especially the teeth lips and periodontium. The study of dental trauma is called dental traumatology.

Anatomy

Dental anatomy
Dental anatomy
Dental anatomy is a field of anatomy dedicated to the study of human tooth structures. The development, appearance, and classification of teeth fall within its purview. Tooth formation begins before birth, and teeth's eventual morphology is dictated during this time...

 is a field of anatomy
Anatomy
Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy , and plant anatomy...

 dedicated to the study of tooth structure. The development, appearance, and classification of teeth fall within its field of study, though dental occlusion
Occlusion (dentistry)
Occlusion, in a dental context, means simply the contact between teeth. More technically, it is the relationship between the maxillary and mandibular teeth when they approach each other, as occurs during chewing or at rest....

, or contact among teeth, does not. Dental anatomy is also a taxonomic
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...

 science as it is concerned with the naming of teeth and their structures. This information serves a practical purpose for dentists, enabling them to easily identify teeth and structures during treatment.

The anatomic crown of a tooth is the area covered in enamel above the cementoenamel junction
Cementoenamel junction
The cementoenamel junction, frequently abbreviated as the CEJ, is an anatomical border identified on a tooth. It is the location where the enamel, which covers the anatomical crown of a tooth, and the cementum, which covers the anatomical root of a tooth, meet...

 (CEJ). The majority of the crown is composed of dentin (dentine in British English) with the pulp chamber in the center. The crown is within bone before eruption
Tooth eruption
Tooth eruption is a process in tooth development in which the teeth enter the mouth and become visible. It is currently believed that the periodontal ligaments play an important role in tooth eruption...

. After eruption, it is almost always visible. The anatomic root is found below the CEJ and is covered with cementum
Cementum
Cementum is a specialized calcified substance covering the root of a tooth. Cementum is excreted by cells called cementoblasts within the root of the tooth and is thickest at the root apex. These cementoblasts develop from undifferentiated mesenchymal cells in the connective tissue of the dental...

. As with the crown, dentin composes most of the root, which normally have pulp canals. A tooth may have multiple roots or just one root (single-rooted teeth). Canines and most premolars, except for maxillary first premolars, usually have one root. Maxillary first premolars and mandibular molars usually have two roots. Maxillary molars usually have three roots. Additional roots are referred to as supernumerary roots
Supernumerary roots
Supernumerary roots is a condition found in teeth there may be a larger number of roots than expected. The most common teeth affected are mandibular canines, premolars, and molars, especially third molars. Canines and most premolars, except for maxillary first premolars, usually have one root. ...

.

Humans usually have 20 primary (deciduous or "baby") teeth and 32 permanent (adult) teeth. Teeth are classified as incisor
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...

s, canines
Canine tooth
In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, fangs, or eye teeth, are relatively long, pointed teeth...

, premolar
Premolar
The premolar teeth or bicuspids are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant, making eight premolars total in the mouth. They have at least two cusps. Premolars can be considered as a 'transitional tooth' during chewing, or...

s, and molars
Molar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....

. Incisors are primarily used for biting pieces from foods such as raw carrot
Carrot
The carrot is a root vegetable, usually orange in colour, though purple, red, white, and yellow varieties exist. It has a crisp texture when fresh...

s or apple
Apple
The apple is the pomaceous fruit of the apple tree, species Malus domestica in the rose family . It is one of the most widely cultivated tree fruits, and the most widely known of the many members of genus Malus that are used by humans. Apple grow on small, deciduous trees that blossom in the spring...

s and peeled but uncut banana
Banana
Banana is the common name for herbaceous plants of the genus Musa and for the fruit they produce. Bananas come in a variety of sizes and colors when ripe, including yellow, purple, and red....

s, while molars are used primarily for grinding foods after they are already in bite size pieces inside the mouth.

Most teeth have identifiable features that distinguish them from others. There are several different notation systems
Dental notation
Dentists, in writing or speech, use several different dental notation systems for associating information to a specific tooth. The three most common systems are the FDI World Dental Federation notation, Universal numbering system , and Palmer notation method...

 to refer to a specific tooth. The three most common systems are the FDI World Dental Federation notation
FDI World Dental Federation notation
FDI World Dental Federation notation is widely used by dentists internationally to associate information to a specific tooth.Developed by the FDI World Dental Federation, World Dental Federation notation is also known as ISO 3950 notation....

, the universal numbering system
Universal numbering system (dental)
The Universal numbering system is a dental notation system for associating information to a specific tooth, and is commonly used in the United States.The designations "left" and "right" on the chart correspond to the patient's left and right, respectively....

, and Palmer notation method. The FDI system is used worldwide, and the universal is used widely in the United States.

Primary teeth

Among deciduous (primary) teeth
Deciduous teeth
Deciduous teeth, otherwise known as reborner teeth, baby teeth, temporary teeth and primary teeth, are the first set of teeth in the growth development of humans and many other mammals. In some Asian countries they are referred to as fall teeth as they will eventually fall out, while in almost all...

, ten are found in the maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...

 (upper jaw) and ten in the mandible (lower jaw), for a total of 20. The dental formula
Dentition
Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, the characteristic arrangement, kind, and number of teeth in a given species at a given age...

 for primary teeth is .

In the primary set of teeth, there are two types of incisors - centrals and laterals, and two types of molars - first and second. All primary teeth are normally later replaced with their permanent counterparts.

Permanent teeth

Among permanent teeth
Permanent teeth
Permanent teeth are the second set of teeth formed in humans. There are thirty-two permanent teeth, consisting of six maxillary and six mandibular molars, four maxillary and four mandibular premolars, two maxillary and two mandibular canines, four maxillary and four mandibular incisors.The first...

, 16 are found in the maxilla and 16 in the mandible, for a total of 32. The dental formula is .

The maxillary teeth are the maxillary central incisor
Maxillary central incisor
The maxillary central incisor is a human tooth in the front upper jaw, or maxilla, and is usually the most visible of all teeth in the mouth. It is located mesial to the maxillary lateral incisor. As with all incisors, their function is for shearing or cutting food during mastication . There are...

, maxillary lateral incisor
Maxillary lateral incisor
The Maxillary lateral incisor is a tooth that is located distally from both maxillary central incisors of the mouth and mesially from both maxillary canines. As with all incisors, their function is for shearing or cutting food during mastication, commonly known as chewing. There are no cusps on...

, maxillary canine
Maxillary canine
The maxillary canine is the tooth located laterally from both maxillary lateral incisors of the mouth but mesial from both maxillary first premolars...

, maxillary first premolar
Maxillary first premolar
The maxillary first premolar is one of two teeth located in the upper jaw, laterally from both the maxillary canines of the mouth but mesial from both maxillary second premolars...

, maxillary second premolar
Maxillary second premolar
The maxillary second premolar is one of two teeth located in the upper jaw, laterally from both the maxillary first premolars of the mouth but mesial from both maxillary first molars...

, maxillary first molar
Maxillary first molar
The maxillary first molar is the tooth located laterally from both the maxillary second premolars of the mouth but mesial from both maxillary second molars....

, maxillary second molar
Maxillary second molar
The maxillary second molar is the tooth located distally from both the maxillary first molars of the mouth but mesial from both maxillary third molars. This is true only in permanent teeth. In deciduous teeth, the maxillary second molar is the last tooth in the mouth and does not have a third...

, and maxillary third molar. The mandibular teeth are the mandibular central incisor
Mandibular central incisor
The mandibular central incisor is the tooth located on the jaw, adjacent to the midline of the face. It is mesial from both mandibular lateral incisors. As with all incisors, its function includes shearing or cutting food during mastication, commonly known as chewing. There are no cusps on the...

, mandibular lateral incisor
Mandibular lateral incisor
The mandibular lateral incisor is the tooth located distally from both mandibular central incisors of the mouth and mesially from both mandibular canines. As with all incisors, their function is for shearing or cutting food during mastication, commonly known as chewing. There are no cusps on...

, mandibular canine
Mandibular canine
The mandibular canine is the tooth located distally from both mandibular lateral incisors of the mouth but mesially from both mandibular first premolars...

, mandibular first premolar
Mandibular first premolar
The mandibular first premolar is the tooth located laterally from both the mandibular canines of the mouth but mesial from both mandibular second premolars. The function of this premolar is similar to that of canines in regard to tearing being the principal action during mastication, commonly...

, mandibular second premolar
Mandibular second premolar
The mandibular second premolar is the tooth located distally from both the mandibular first premolars of the mouth but mesial from both mandibular first molars. The function of this premolar is assist the mandibular first molar during mastication, commonly known as chewing. Mandibular second...

, mandibular first molar
Mandibular first molar
The mandibular first molar or six-year molar is the tooth located distally from both the mandibular second premolars of the mouth but mesial from both mandibular second molars...

, mandibular second molar
Mandibular second molar
The mandibular second molar is the tooth located distally from both the mandibular first molars of the mouth but mesial from both mandibular third molars. This is true only in permanent teeth...

, and mandibular third molar. Third molars are commonly called "wisdom teeth" and may never erupt into the mouth or form at all. If any additional teeth form, for example, fourth and fifth molars, which are rare, they are referred to as supernumerary teeth (hyperdontia)
Hyperdontia
Hyperdontia is the condition of having supernumerary teeth, or teeth which appear in addition to the regular number of teeth.-Types:Supernumerary teeth can be classified by shape and by position...

. Development of fewer than the usual number of teeth is called hypodontia
Hypodontia
In dentistry, hypodontia is the condition at which the patient has missing teeth as a result of their failure to develop. Hypodontia describes a situation where the patient is missing up to 6 teeth, excluding the 3rd molars. Missing third molars occur in 9-30% of population...

.

Enamel

Enamel is the hardest and most highly mineralized substance of the body. It is one of the four major tissues which make up the tooth, along with dentin
Dentin
Dentine is a calcified tissue of the body, and along with enamel, cementum, and pulp is one of the four major components of teeth. Usually, it is covered by enamel on the crown and cementum on the root and surrounds the entire pulp...

, cementum
Cementum
Cementum is a specialized calcified substance covering the root of a tooth. Cementum is excreted by cells called cementoblasts within the root of the tooth and is thickest at the root apex. These cementoblasts develop from undifferentiated mesenchymal cells in the connective tissue of the dental...

, and dental pulp. It is normally visible and must be supported by underlying dentin. 96% of enamel consists of mineral, with water and organic material comprising the rest. The normal color of enamel varies from light yellow to grayish white. At the edges of teeth where there is no dentin underlying the enamel, the color sometimes has a slightly blue tone. Since enamel is semitranslucent, the color of dentin and any restorative dental material underneath the enamel strongly affects the appearance of a tooth. Enamel varies in thickness over the surface of the tooth and is often thickest at the cusp
Cusp (dentistry)
A cusp is an occlusal or incisal eminence on a tooth.Canine teeth, otherwise known as cuspids, each possess a single cusp, while premolars, otherwise known as bicuspids, possess two each. Molars normally possess either four or five cusps...

, up to 2.5mm, and thinnest at its border, which is seen clinically as the CEJ.

Enamel's primary mineral is hydroxylapatite
Hydroxylapatite
Hydroxylapatite, also called hydroxyapatite , is a naturally occurring mineral form of calcium apatite with the formula Ca53, but is usually written Ca1062 to denote that the crystal unit cell comprises two entities. Hydroxylapatite is the hydroxyl endmember of the complex apatite group...

, which is a crystal
Crystal
A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...

line calcium phosphate
Calcium phosphate
Calcium phosphate is the name given to a family of minerals containing calcium ions together with orthophosphates , metaphosphates or pyrophosphates and occasionally hydrogen or hydroxide ions ....

. The large amount of minerals in enamel accounts not only for its strength but also for its brittleness. Dentin, which is less mineralized and less brittle, compensates for enamel and is necessary as a support. Unlike dentin and bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...

, enamel does not contain collagen
Collagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...

. Instead, it has two unique classes of protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

s called amelogenin
Amelogenin
Amelogenin is a protein found in developing tooth enamel, and it belongs to a family of extracellular matrix proteins. Developing enamel contains about 30% protein, and 90% of this is amelogenins...

s and enamelin
Enamelin
Enamelin was described in older literature as an EDTA soluble enamel protein. It accounts for the organic portion of enamel, which represents 4% of enamel's mass. It turned out in recent research to be albumin derived from blood contamination....

s. While the role of these proteins is not fully understood, it is believed that they aid in the development of enamel by serving as framework support among other functions.

Dentin

Dentin is the substance between enamel or cementum and the pulp chamber. It is secreted by the odontoblasts of the dental pulp. The formation of dentin is known as dentinogenesis
Dentinogenesis
Dentinogenesis is the formation of dentin, a substance that forms the majority of teeth. Dentinogenesis is performed by odontoblasts, which are a special type of biological cells on the outside of dental pulps, and it begins at the late bell stage of a developing tooth...

. The porous, yellow-hued material is made up of 70% inorganic materials, 20% organic materials, and 10% water by weight. Because it is softer than enamel, it decays more rapidly and is subject to severe cavities if not properly treated, but dentin still acts as a protective layer and supports the crown of the tooth.

Dentin is a mineralized connective tissue
Connective tissue
"Connective tissue" is a fibrous tissue. It is one of the four traditional classes of tissues . Connective Tissue is found throughout the body.In fact the whole framework of the skeleton and the different specialized connective tissues from the crown of the head to the toes determine the form of...

 with an organic matrix of collagenous proteins. Dentin has microscopic channels, called dentinal tubules, which radiate outward through the dentin from the pulp cavity to the exterior cementum or enamel border. The diameter of these tubules range from 2.5 μm near the pulp, to 1.2 μm in the midportion, and 900nm near the dentino-enamel junction. Although they may have tiny side-branches, the tubules do not intersect with each other. Their length is dictated by the radius of the tooth. The three dimensional configuration of the dentinal tubules is genetically determined.

Cementum

Cementum is a specialized bone like substance covering the root of a tooth. It is approximately 45% inorganic material (mainly hydroxyapatite), 33% organic material (mainly collagen
Collagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...

) and 22% water. Cementum is excreted by cementoblast
Cementoblast
A cementoblast is a biological cell that forms from the follicular cells around the root of a tooth, and whose biological function is cementogenesis, which is the creation of cementum ....

s within the root of the tooth and is thickest at the root apex. Its coloration is yellowish and it is softer than either dentin or enamel. The principal role of cementum is to serve as a medium by which the periodontal ligament
Periodontal ligament
The periodontal fiber or periodontal ligament, commonly abbreviated as the PDL, is a group of specialized connective tissue fibers that essentially attach a tooth to the alveolar bone within which it sits...

s can attach to the tooth for stability. At the cementoenamel junction, the cementum is acellular due to its lack of cellular components, and this acellular type covers at least ⅔ of the root. The more permeable form of cementum, cellular cementum, covers about ⅓ of the root apex.

Pulp

The dental pulp is the central part of the tooth filled with soft connective tissue. This tissue contains blood vessels and nerves that enter the tooth from a hole at the apex of the root. Along the border between the dentin and the pulp are odontoblasts, which initiate the formation of dentin. Other cells in the pulp include fibroblasts, preodontoblasts, macrophage
Macrophage
Macrophages are cells produced by the differentiation of monocytes in tissues. Human macrophages are about in diameter. Monocytes and macrophages are phagocytes. Macrophages function in both non-specific defense as well as help initiate specific defense mechanisms of vertebrate animals...

s and T lymphocytes. The pulp is commonly called "the nerve" of the tooth.

Development

Tooth development is the complex process by which teeth form from embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

nic cells
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

, grow
Cell growth
The term cell growth is used in the contexts of cell development and cell division . When used in the context of cell division, it refers to growth of cell populations, where one cell grows and divides to produce two "daughter cells"...

, and erupt into the mouth
Mouth
The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....

. Although many diverse species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 have teeth, non-human tooth development is largely the same as in humans. For human
Human
Humans are the only living species in the Homo genus...

 teeth to have a healthy oral environment, enamel
Tooth enamel
Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...

, dentin
Dentin
Dentine is a calcified tissue of the body, and along with enamel, cementum, and pulp is one of the four major components of teeth. Usually, it is covered by enamel on the crown and cementum on the root and surrounds the entire pulp...

, cementum
Cementum
Cementum is a specialized calcified substance covering the root of a tooth. Cementum is excreted by cells called cementoblasts within the root of the tooth and is thickest at the root apex. These cementoblasts develop from undifferentiated mesenchymal cells in the connective tissue of the dental...

, and the periodontium
Periodontium
Periodontium refers to the specialized tissues that both surround and support the teeth, maintaining them in the maxillary and mandibular bones. The word comes from the Greek terms peri-, meaning "around" and -odons, meaning "tooth." Literally taken, it means that which is "around the tooth"...

 must all develop during appropriate stages of fetal development
Fetal development
Prenatal or antenatal development is the process in which a human embryo or fetus gestates during pregnancy, from fertilization until birth. Often, the terms fetal development, foetal development, or embryology are used in a similar sense.After fertilization the embryogenesis starts...

. Primary teeth
Deciduous teeth
Deciduous teeth, otherwise known as reborner teeth, baby teeth, temporary teeth and primary teeth, are the first set of teeth in the growth development of humans and many other mammals. In some Asian countries they are referred to as fall teeth as they will eventually fall out, while in almost all...

 start to form between the sixth and eighth weeks in utero
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...

, and permanent teeth
Permanent teeth
Permanent teeth are the second set of teeth formed in humans. There are thirty-two permanent teeth, consisting of six maxillary and six mandibular molars, four maxillary and four mandibular premolars, two maxillary and two mandibular canines, four maxillary and four mandibular incisors.The first...

 begin to form in the twentieth week in utero. If teeth do not start to develop at or near these times, they will not develop at all.

A significant amount of research has focused on determining the processes that initiate tooth development. It is widely accepted that there is a factor within the tissues of the first branchial arch
Branchial arch
In the development of vertebrate animals, the pharyngeal arches are anlage for a multitude of structures. In humans, they develop during the fourth week in utero as a series of mesodermal outpouchings on the left and right sides of the developing pharynx...

 that is necessary for the development of teeth.

Tooth development is commonly divided into the following stages: the bud stage, the cap, the bell, and finally maturation. The staging of tooth development is an attempt to categorize changes that take place along a continuum; frequently it is difficult to decide what stage should be assigned to a particular developing tooth. This determination is further complicated by the varying appearance of different histologic sections of the same developing tooth, which can appear to be different stages.

The tooth bud (sometimes called the tooth germ) is an aggregation of cells
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

 that eventually forms a tooth. It is organized into three parts: the enamel organ
Enamel organ
The enamel organ, also known as dental organ, is a cellular aggregation seen in histologic sections of a developing tooth. It lies above a condensation of ectomesenchymal cells called the dental papilla...

, the dental papilla
Dental papilla
The dental papilla is a condensation of ectomesenchymal cells called odontoblasts, seen in histologic sections of a developing tooth. It lies below a cellular aggregation known as the enamel organ. The dental papilla appears after 8-10 weeks intra uteral life...

 and the dental follicle
Dental follicle
The dental follicle is a sac containing the developing tooth and its odontogenic organ. The dental follicle differentiates into the periodontal ligament. In addition, it may be the precursor of other cells of the periodontium, including osteoblasts and cementoblasts...

. The enamel organ is composed of the outer enamel epithelium
Outer enamel epithelium
The outer enamel epithelium, also known as the external enamel epithelium, is a layer of cuboidal cells located on the periphery of the enamel organ in a developing tooth. This layer is first seen during the bell stage....

, inner enamel epithelium
Inner enamel epithelium
The inner enamel epithelium, also known as the internal enamel epithelium, is a layer of cells located on the rim nearest the dental papilla of the enamel organ in a developing tooth. This layer is first seen during the bell stage....

, stellate reticulum
Stellate reticulum
The stellate reticulum is a group of cells located in the center of the enamel organ of a developing tooth. These cells are star shaped and synthesize glycosaminoglycans. As glycosamingoglycans are produced, water is drawn in between the cells and stretch them apart...

 and stratum intermedium
Stratum intermedium
The stratum intermedium in a developing tooth is a layer of two or three cells between the inner enamel epithelium and the newly forming cells of the stellate reticulum. It first appears during the early bell stage of tooth development, at around the 14th week of intrauterine life. The stratum...

. These cells give rise to ameloblast
Ameloblast
Ameloblasts are cells, present only during tooth development, that deposit tooth enamel, the hard outermost layer of the tooth that forms the chewing surface....

s, which produce enamel and the reduced enamel epithelium
Reduced enamel epithelium
The reduced enamel epithelium, sometimes called reduced dental epithelium, overlies a developing tooth and is formed by two layers: a layer of ameloblast cells and the adjacent layer of cuboidal cells from the dental lamina. As the cells of the reduced enamel epithelium degenerate, the tooth is...

. The growth of cervical loop
Cervical loop
The cervical loop is the location on an enamel organ in a developing tooth where the outer enamel epithelium and the inner enamel epithelium join. The cervical loop is a histologic term indicating a specific epithelial structure at the apical side of the tooth germ, consisting of loosely aggregated...

 cells into the deeper tissues forms Hertwig's Epithelial Root Sheath
Hertwig's epithelial root sheath
The Hertwig's epithelial root sheath is a proliferation of epithelial cells located at the cervical loop of the enamel organ in a developing tooth. Hertwig's epithelial root sheath initiates the formation of dentin in the root of a tooth by causing the differentiation of odontoblasts from the...

, which determines a tooth's root shape. The dental papilla contains cells that develop into odontoblast
Odontoblast
In vertebrates, an odontoblast is a biological cell of neural crest origin that is part of the outer surface of the dental pulp, and whose biological function is dentinogenesis, which is the creation of dentin, the substance under the tooth enamel....

s, which are dentin-forming cells. Additionally, the junction between the dental papilla and inner enamel epithelium determines the crown shape of a tooth. The dental follicle gives rise to three important entities: cementoblast
Cementoblast
A cementoblast is a biological cell that forms from the follicular cells around the root of a tooth, and whose biological function is cementogenesis, which is the creation of cementum ....

s, osteoblast
Osteoblast
Osteoblasts are mononucleate cells that are responsible for bone formation; in essence, osteoblasts are specialized fibroblasts that in addition to fibroblastic products, express bone sialoprotein and osteocalcin.Osteoblasts produce a matrix of osteoid, which is composed mainly of Type I collagen...

s, and fibroblast
Fibroblast
A fibroblast is a type of cell that synthesizes the extracellular matrix and collagen, the structural framework for animal tissues, and plays a critical role in wound healing...

s. Cementoblasts form the cementum of a tooth. Osteoblasts give rise to the alveolar bone
Alveolar process of maxilla
The alveolar process is the thickened ridge of bone that contains the tooth sockets on bones that bear teeth. It is also referred to as the alveolar bone. In humans, the tooth-bearing bones are the maxilla and the mandible...

 around the roots of teeth. Fibroblasts develop the periodontal ligament
Periodontal ligament
The periodontal fiber or periodontal ligament, commonly abbreviated as the PDL, is a group of specialized connective tissue fibers that essentially attach a tooth to the alveolar bone within which it sits...

s which connect teeth to the alveolar bone through cementum.

Eruption

Tooth eruption in humans is a process in tooth development in which the teeth enter the mouth and become visible. Current research indicates that the periodontal ligaments play an important role in tooth eruption. Primary teeth erupt into the mouth from around six months until two years of age. These teeth are the only ones in the mouth until a person is about six years old. At that time, the first permanent tooth erupts. This stage, during which a person has a combination of primary and permanent teeth, is known as the mixed stage. The mixed stage lasts until the last primary tooth is lost and the remaining permanent teeth erupt into the mouth.

There have been many theories about the cause of tooth eruption. One theory proposes that the developing root of a tooth pushes it into the mouth. Another, known as the cushioned hammock theory, resulted from microscopic study of teeth, which was thought to show a ligament
Ligament
In anatomy, the term ligament is used to denote any of three types of structures. Most commonly, it refers to fibrous tissue that connects bones to other bones and is also known as articular ligament, articular larua, fibrous ligament, or true ligament.Ligament can also refer to:* Peritoneal...

 around the root. It was later discovered that the "ligament" was merely an artifact created in the process of preparing the slide. Currently, the most widely held belief is that the periodontal ligaments provide the main impetus for the process.

The onset of primary tooth loss has been found to correlate strongly with somatic and psychological criteria of school readiness.

Supporting structures

The periodontium
Periodontium
Periodontium refers to the specialized tissues that both surround and support the teeth, maintaining them in the maxillary and mandibular bones. The word comes from the Greek terms peri-, meaning "around" and -odons, meaning "tooth." Literally taken, it means that which is "around the tooth"...

 is the supporting structure of a tooth, helping to attach the tooth to surrounding tissues and to allow sensations of touch and pressure. It consists of the cementum, periodontal ligaments, alveolar bone, and gingiva
Gingiva
The gingiva , or gums, consists of the mucosal tissue that lies over the mandible and maxilla inside the mouth.-General description:...

. Of these, cementum is the only one that is a part of a tooth. Periodontal ligaments connect the alveolar bone to the cementum. Alveolar bone surrounds the roots of teeth to provide support and creates what is commonly called an alveolus
Dental alveolus
Dental alveolus are sockets in the jaws in which the roots of teeth are held in the alveolar process of maxilla with the periodontal ligament. The lay term for dental alveoli is tooth sockets...

, or "socket". Lying over the bone is the gingiva
Gingiva
The gingiva , or gums, consists of the mucosal tissue that lies over the mandible and maxilla inside the mouth.-General description:...

 or gum, which is readily visible in the mouth.

Periodontal ligaments

The periodontal ligament
Periodontal ligament
The periodontal fiber or periodontal ligament, commonly abbreviated as the PDL, is a group of specialized connective tissue fibers that essentially attach a tooth to the alveolar bone within which it sits...

 is a specialized connective tissue
Connective tissue
"Connective tissue" is a fibrous tissue. It is one of the four traditional classes of tissues . Connective Tissue is found throughout the body.In fact the whole framework of the skeleton and the different specialized connective tissues from the crown of the head to the toes determine the form of...

 that attaches the cementum of a tooth to the alveolar bone. This tissue covers the root of the tooth within the bone. Each ligament has a width of 0.15–0.38mm, but this size decreases over time. The functions of the periodontal ligaments include attachment of the tooth to the bone, support for the tooth, formation and resorption
Bone resorption
Bone resorption is the process by which osteoclasts break down bone and release the minerals, resulting in a transfer of calcium from bone fluid to the blood....

 of bone during tooth movement, sensation, and eruption. The cells of the periodontal ligaments include osteoblasts, osteoclasts, fibroblasts, macrophages, cementoblasts, and epithelial cell rests of Malassez
Epithelial cell rests of Malassez
In dentistry, the epithelial cell rests of Malassez or epithelial rests of Malassez are part of the periodontal ligament cells around a tooth. They are discrete clusters of residual cells from Hertwig's epithelial root sheath that didn't completely disappear...

. Consisting of mostly Type I and III collagen
Collagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...

, the fibers are grouped in bundles and named according to their location. The groups of fibers are named alveolar crest, horizontal, oblique, periapical, and interradicular fibers. The nerve supply generally enters from the bone apical to the tooth and forms a network around the tooth toward the crest of the gingiva. When pressure is exerted on a tooth, such as during chewing or biting, the tooth moves slightly in its socket and puts tension on the periodontal ligaments. The nerve fibers can then send the information to the central nervous system for interpretation.

Alveolar bone

The alveolar bone is the bone of the jaw which forms the alveolus around teeth. Like any other bone in the human body, alveolar bone is modified throughout life. Osteoblast
Osteoblast
Osteoblasts are mononucleate cells that are responsible for bone formation; in essence, osteoblasts are specialized fibroblasts that in addition to fibroblastic products, express bone sialoprotein and osteocalcin.Osteoblasts produce a matrix of osteoid, which is composed mainly of Type I collagen...

s create bone and osteoclast
Osteoclast
An osteoclast is a type of bone cell that removes bone tissue by removing its mineralized matrix and breaking up the organic bone . This process is known as bone resorption. Osteoclasts were discovered by Kolliker in 1873...

s destroy it, especially if force is placed on a tooth. As is the case when movement of teeth is attempted through orthodontics, an area of bone under compressive force
Force
In physics, a force is any influence that causes an object to undergo a change in speed, a change in direction, or a change in shape. In other words, a force is that which can cause an object with mass to change its velocity , i.e., to accelerate, or which can cause a flexible object to deform...

 from a tooth moving toward it has a high osteoclast level, resulting in bone resorption
Bone resorption
Bone resorption is the process by which osteoclasts break down bone and release the minerals, resulting in a transfer of calcium from bone fluid to the blood....

. An area of bone receiving tension
Tension (mechanics)
In physics, tension is the magnitude of the pulling force exerted by a string, cable, chain, or similar object on another object. It is the opposite of compression. As tension is the magnitude of a force, it is measured in newtons and is always measured parallel to the string on which it applies...

 from periodontal ligaments attached to a tooth moving away from it has a high number of osteoblasts, resulting in bone formation.

Gingiva

The gingiva
Gingiva
The gingiva , or gums, consists of the mucosal tissue that lies over the mandible and maxilla inside the mouth.-General description:...

 ("gums") is the mucosal tissue that overlays the jaws. There are three different types of epithelium associated with the gingiva: gingival, junctional, and sulcular epithelium. These three types form from a mass of epithelial cells known as the epithelial cuff between the tooth and the mouth. The gingival epithelium is not associated directly with tooth attachment and is visible in the mouth. The junctional epithelium, composed of the basal lamina
Basal lamina
The basal lamina is a layer of extracellular matrix secreted by the epithelial cells, on which the epithelium sits. It is often confused with the basement membrane, and sometimes used inconsistently in the literature, see below....

 and hemidesmosome
Hemidesmosome
Hemidesmosomes are very small stud- or rivet-like structures on the inner basal surface of keratinocytes in the epidermis of skin. They are similar in form to desmosomes when visualized by electron microscopy. While desmosomes link two cells together, hemidesmosomes attach one cell to the...

s, forms an attachment to the tooth. The sulcular epithelium is nonkeratinized stratified squamous
Squamous epithelium
In anatomy, squamous epithelium is an epithelium characterised by its most superficial layer consisting of flat, scale-like cells called squamous epithelial cells...

 tissue on the gingiva which touches but is not attached to the tooth.

Plaque

Plaque is a biofilm
Biofilm
A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...

 consisting of large quantities of various bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 that form on teeth. If not removed regularly, plaque buildup can lead to dental cavities (caries) or periodontal problems such as gingivitis
Gingivitis
Gingivitis is a term used to describe non-destructive periodontal disease. The most common form of gingivitis is in response to bacterial biofilms adherent to tooth surfaces, termed plaque-induced gingivitis, and is the most common form of periodontal disease...

. Given time, plaque can mineralize along the gingiva, forming tartar
Calculus (dental)
In dentistry, calculus or tartar is a form of hardened dental plaque. It is caused by the continual accumulation of minerals from saliva on plaque on the teeth...

. The microorganism
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...

s that form the biofilm are almost entirely bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 (mainly streptococcus
Streptococcus
Streptococcus is a genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the lactic acid bacteria group. Cellular division occurs along a single axis in these bacteria, and thus they grow in chains or pairs, hence the name — from Greek στρεπτος streptos, meaning...

 and anaerobes
Anaerobic organism
An anaerobic organism or anaerobe is any organism that does not require oxygen for growth. It could possibly react negatively and may even die if oxygen is present...

), with the composition varying by location in the mouth. Streptococcus mutans
Streptococcus mutans
Streptococcus mutans is a facultatively aerobic, Gram-positive coccus-shaped bacterium commonly found in the human oral cavity and is a significant contributor to tooth decay.The microbe was first described by J Kilian Clarke in 1924.-Introduction:...

is the most important bacterium associated with dental caries.

Certain bacteria in the mouth live off the remains of foods, especially sugar
Sugar
Sugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...

s and starches. In the absence of oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 they produce lactic acid
Lactic acid
Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...

, which dissolves
Solvation
Solvation, also sometimes called dissolution, is the process of attraction and association of molecules of a solvent with molecules or ions of a solute...

 the calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

 and phosphorus
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...

 in the enamel. This process, known as "demineralisation", leads to tooth destruction. Saliva
Saliva
Saliva , referred to in various contexts as spit, spittle, drivel, drool, or slobber, is the watery substance produced in the mouths of humans and most other animals. Saliva is a component of oral fluid. In mammals, saliva is produced in and secreted from the three pairs of major salivary glands,...

 gradually neutralises the acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...

s which cause the pH of the tooth surface to rise above the critical pH. This causes 'remineralisation
Remineralisation
In biogeochemistry, remineralisation refers to the transformation of organic molecules to inorganic forms, typically mediated by biological activity....

', the return of the dissolved minerals to the enamel. If there is sufficient time between the intake of foods then the impact is limited and the teeth can repair themselves. Saliva is unable to penetrate through plaque, however, to neutralize the acid produced by the bacteria.

Caries (cavities)


Dental caries, also described as "tooth decay" or "dental cavities", is an infectious disease which damages the structures of teeth. The disease can lead to pain
Pain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...

, tooth loss
Tooth loss
Tooth loss is when one or more teeth come loose and fall out. Tooth loss is normal for deciduous teeth , when they are replaced by a person's adult teeth. Otherwise, losing teeth is undesirable and is the result of injury or disease, such as mouth trauma, tooth injury, tooth decay, and gum disease...

, infection, and, in severe cases, death. Dental caries has a long history, with evidence showing the disease was present in the Bronze
Bronze Age
The Bronze Age is a period characterized by the use of copper and its alloy bronze as the chief hard materials in the manufacture of some implements and weapons. Chronologically, it stands between the Stone Age and Iron Age...

, Iron
Iron Age
The Iron Age is the archaeological period generally occurring after the Bronze Age, marked by the prevalent use of iron. The early period of the age is characterized by the widespread use of iron or steel. The adoption of such material coincided with other changes in society, including differing...

, and Middle
Middle Ages
The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...

 ages but also prior to the neolithic
Neolithic
The Neolithic Age, Era, or Period, or New Stone Age, was a period in the development of human technology, beginning about 9500 BC in some parts of the Middle East, and later in other parts of the world. It is traditionally considered as the last part of the Stone Age...

 period. The largest increases in the prevalence of caries have been associated with diet changes. Today, caries remains one of the most common diseases throughout the world. In the United States, dental caries is the most common chronic
Chronic (medicine)
A chronic disease is a disease or other human health condition that is persistent or long-lasting in nature. The term chronic is usually applied when the course of the disease lasts for more than three months. Common chronic diseases include asthma, cancer, diabetes and HIV/AIDS.In medicine, the...

 childhood disease, being at least five times more common than asthma
Asthma
Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...

. Countries that have experienced an overall decrease in cases of tooth decay continue to have a disparity in the distribution of the disease. Among children in the United States and Europe, 60-80% of cases of dental caries occur in 20% of the population.

Tooth decay is caused by certain types of acid-producing bacteria which cause the most damage in the presence of fermentable
Fermentation (food)
Fermentation in food processing typically is the conversion of carbohydrates to alcohols and carbon dioxide or organic acids using yeasts, bacteria, or a combination thereof, under anaerobic conditions. Fermentation in simple terms is the chemical conversion of sugars into ethanol...

 carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...

s such as sucrose
Sucrose
Sucrose is the organic compound commonly known as table sugar and sometimes called saccharose. A white, odorless, crystalline powder with a sweet taste, it is best known for its role in human nutrition. The molecule is a disaccharide composed of glucose and fructose with the molecular formula...

, fructose
Fructose
Fructose, or fruit sugar, is a simple monosaccharide found in many plants. It is one of the three dietary monosaccharides, along with glucose and galactose, that are absorbed directly into the bloodstream during digestion. Fructose was discovered by French chemist Augustin-Pierre Dubrunfaut in 1847...

, and glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

. The resulting acidic levels in the mouth affect teeth because a tooth's special mineral content causes it to be sensitive to low pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

. Depending on the extent of tooth destruction, various treatments can be used to restore
Dental restoration
A dental restoration or dental filling is a dental restorative material used to restore the function, integrity and morphology of missing tooth structure. The structural loss typically results from caries or external trauma. It is also lost intentionally during tooth preparation to improve the...

 teeth to proper form, function, and aesthetics
Aesthetics
Aesthetics is a branch of philosophy dealing with the nature of beauty, art, and taste, and with the creation and appreciation of beauty. It is more scientifically defined as the study of sensory or sensori-emotional values, sometimes called judgments of sentiment and taste...

, but there is no known method to regenerate
Regeneration (biology)
In biology, regeneration is the process of renewal, restoration, and growth that makes genomes, cells, organs, organisms, and ecosystems resilient to natural fluctuations or events that cause disturbance or damage. Every species is capable of regeneration, from bacteria to humans. At its most...

 large amounts of tooth structure. Instead, dental health organizations advocate preventative and prophylactic measures, such as regular oral hygiene
Oral hygiene
Teeth cleaning is part of oral hygiene and involves the removal of dental plaque from teeth with the intention of preventing cavities , gingivitis, and periodontal disease. People routinely clean their own teeth by brushing and interdental cleaning, and dental hygienists can remove hardened...

 and dietary modifications, to avoid dental caries.

Tooth care

Oral hygiene is the practice of keeping the mouth clean and is a means of preventing dental caries, gingivitis
Gingivitis
Gingivitis is a term used to describe non-destructive periodontal disease. The most common form of gingivitis is in response to bacterial biofilms adherent to tooth surfaces, termed plaque-induced gingivitis, and is the most common form of periodontal disease...

, periodontal disease
Periodontal disease
Periodontitis is a set of inflammatory diseases affecting the periodontium, i.e., the tissues that surround and support the teeth. Periodontitis involves progressive loss of the alveolar bone around the teeth, and if left untreated, can lead to the loosening and subsequent loss of teeth...

, bad breath
Halitosis
Halitosis is a term used to describe noticeably unpleasant odors exhaled in breathing. Halitosis is estimated to be the third most frequent reason for seeking dental aid, following tooth decay and periodontal disease.- General :...

, and other dental disorders. It consists of both professional and personal care. Regular cleanings, usually done by dentists and dental hygienists, remove tartar
Calculus (dental)
In dentistry, calculus or tartar is a form of hardened dental plaque. It is caused by the continual accumulation of minerals from saliva on plaque on the teeth...

 (mineralized plaque) that may develop even with careful brushing
Tooth brushing
Tooth brushing is the act of cleaning teeth with a toothbrush.Modern medical research has shown that brushing teeth properly can prevent cavities, and periodontal, or gum disease, which causes at least one-third of adult tooth loss. If teeth are not brushed correctly and frequently, it could lead...

 and flossing. Professional cleaning includes tooth scaling, using various instruments or devices to loosen and remove deposits from teeth.

The purpose of cleaning teeth is to remove plaque, which consists mostly of bacteria. Healthcare professionals recommend regular brushing twice a day (in the morning and in the evening, or after meals) in order to prevent formation of plaque and tartar. A toothbrush is able to remove most plaque, except in areas between teeth. As a result, flossing is also considered a necessity to maintain oral hygiene. When used correctly, dental floss removes plaque from between teeth and at the gum line, where periodontal disease
Periodontal disease
Periodontitis is a set of inflammatory diseases affecting the periodontium, i.e., the tissues that surround and support the teeth. Periodontitis involves progressive loss of the alveolar bone around the teeth, and if left untreated, can lead to the loosening and subsequent loss of teeth...

 often begins and could develop caries. Electric toothbrush
Electric toothbrush
An electric toothbrush is a toothbrush that uses electric power supplied usually by a battery to move the brush head rapidly, either oscillating side to side, or rotation-oscillation .- History :...

es are not considered more effective than manual brushes for most people. The most important advantage of electric toothbrushes is their ability to aid people with dexterity difficulties, such as those associated with rheumatoid arthritis
Rheumatoid arthritis
Rheumatoid arthritis is a chronic, systemic inflammatory disorder that may affect many tissues and organs, but principally attacks synovial joints. The process produces an inflammatory response of the synovium secondary to hyperplasia of synovial cells, excess synovial fluid, and the development...

.

Fluoride therapy
Fluoride therapy
Fluoride therapy is the delivery of fluoride to the teeth topically or systemically in order to prevent tooth decay which results in cavities. Most commonly, fluoride is applied topically to the teeth using gels, varnishes, toothpaste/dentifrices or mouth rinse. Systemic delivery involves...

 is often recommended to protect against dental caries. Water fluoridation
Water fluoridation
Water fluoridation is the controlled addition of fluoride to a public water supply to reduce tooth decay. Fluoridated water has fluoride at a level that is effective for preventing cavities; this can occur naturally or by adding fluoride...

 and fluoride
Fluoride
Fluoride is the anion F−, the reduced form of fluorine when as an ion and when bonded to another element. Both organofluorine compounds and inorganic fluorine containing compounds are called fluorides. Fluoride, like other halides, is a monovalent ion . Its compounds often have properties that are...

 supplements decrease the incidence of dental caries. Fluoride helps prevent dental decay by binding to the hydroxyapatite crystals in enamel. The incorporated fluoride makes enamel more resistant to demineralization and thus more resistant to decay. Topical fluoride, such as a fluoride toothpaste
Toothpaste
Toothpaste is a paste or gel dentifrice used with a toothbrush as an accessory to clean and maintain the aesthetics and health of teeth. Toothpaste is used to promote oral hygiene: it serves as an abrasive that aids in removing the dental plaque and food from the teeth, assists in suppressing...

 or mouthwash
Mouthwash
Mouthwash or mouth rinse is a product used to enhance oral hygiene. Some manufacturers of mouthwash claim that antiseptic and anti-plaque mouth rinse kill the bacterial plaque causing cavities, gingivitis, and bad breath. Anti-cavity mouth rinse uses fluoride to protect against tooth decay...

, is also recommended to protect teeth surfaces. Many dentists include application of topical fluoride solutions as part of routine cleanings.

Restorations

After a tooth has been damaged or destroyed, restoration
Dental restoration
A dental restoration or dental filling is a dental restorative material used to restore the function, integrity and morphology of missing tooth structure. The structural loss typically results from caries or external trauma. It is also lost intentionally during tooth preparation to improve the...

 of the missing structure can be achieved with a variety of treatments. Restorations may be created from a variety of materials, including glass ionomer
Glass ionomer cement
A Glass Ionomer Cement is a dental restorative material used in dentistry for filling teeth and luting cements. These materials are based on the reaction of silicate glass powder and polyalkenoic acid...

, amalgam
Amalgam (dentistry)
Amalgam is an alloy containing mercury. The term is commonly used for the amalgam employed as material for dental fillings, which consists of mercury , silver , tin , copper , and other trace metals...

, gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

, porcelain
Dental porcelain
Dental porcelain is a porcelain used by a dental technician to create biocompatible lifelike crowns, bridges, and veneers for the patient...

, and composite
Dental composite
Dental composite resins are types of synthetic resins which are used in dentistry as restorative material or adhesives. Synthetic resins evolved as restorative materials since they were insoluble, aesthetic, insensitive to dehydration, easy to manipulate and reasonably inexpensive...

. Small restorations placed inside a tooth are referred to as "intracoronal restorations". These restorations may be formed directly in the mouth or may be cast using the lost-wax technique, such as for some inlays and onlays. When larger portions of a tooth are lost, an "extracoronal restoration" may be fabricated, such as a crown
Crown (dentistry)
A crown is a type of dental restoration which completely caps or encircles a tooth or dental implant. Crowns are often needed when a large cavity threatens the ongoing health of a tooth. They are typically bonded to the tooth using a dental cement. Crowns can be made from many materials, which...

 or a veneer
Veneer (dentistry)
In dentistry, a veneer is a thin layer of restorative material placed over a tooth surface, either to improve the aesthetics of a tooth, or to protect a damaged tooth surface. There are two main types of material used to fabricate a veneer, composite and dental porcelain...

, to restore the involved tooth.

When a tooth is lost, dentures
Dentures
Dentures are prosthetic devices constructed to replace missing teeth, and which are supported by surrounding soft and hard tissues of the oral cavity. Conventional dentures are removable, however there are many different denture designs, some which rely on bonding or clasping onto teeth or dental...

, bridges
Bridge (dentistry)
A bridge, also known as a fixed partial denture, is a dental restoration used to replace a missing tooth by joining permanently to adjacent teeth or dental implants....

, or implants
Dental implant
A dental implant is a "root" device, usually made of titanium, used in dentistry to support restorations that resemble a tooth or group of teeth to replace missing teeth....

 may be used as replacements. Dentures are usually the least costly whereas implants are usually the most expensive. Dentures may replace complete arches of the mouth or only a partial number of teeth. Bridges replace smaller spaces of missing teeth and use adjacent teeth to support the restoration. Dental implants may be used to replace a single tooth or a series of teeth. Though implants are the most expensive treatment option, they are often the most desirable restoration because of their aesthetics and function. To improve the function of dentures, implants may be used as support.

Abnormalities

Tooth abnormalities may be categorized according to whether they have environmental or developmental causes. While environmental abnormalities may appear to have an obvious cause, there may not appear to be any known cause for some developmental abnormalities. Environmental forces may affect teeth during development, destroy tooth structure after development, discolor teeth at any stage of development, or alter the course of tooth eruption. Developmental abnormalities most commonly affect the number, size, shape, and structure of teeth.

Alteration during tooth development

Tooth abnormalities caused by environmental factors during tooth development have long-lasting effects. Enamel and dentin do not regenerate after they mineralize initially. Enamel hypoplasia
Enamel hypoplasia
Enamel hypoplasia is the defect of the teeth in which the tooth enamel is hard but thin and deficient in amount. This is caused by defective enamel matrix formation with a deficiency in the cementing substance....

 is a condition in which the amount of enamel formed is inadequate. This results either in pits and grooves in areas of the tooth or in widespread absence of enamel. Diffuse opacities of enamel does not affect the amount of enamel but changes its appearance. Affected enamel has a different translucency than the rest of the tooth. Demarcated opacities of enamel have sharp boundaries where the translucency decreases and manifest a white, cream, yellow, or brown color. All these may be caused by a systemic event, such as an exanthem
Exanthem
An exanthem is a widespread rash usually occurring in children. Exanthems can be caused by toxins or drugs, microorganisms, or can result from autoimmune disease.It can be contrasted with an enanthem.-Types:...

atous fever
Fever
Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...

. Turner's hypoplasia
Turner's hypoplasia
Turner's hypoplasia is an abnormality found in teeth. Its appearance is variable, though usually is manifested as a portion of missing or diminished enamel on permanent teeth...

 is a portion of missing or diminished enamel on a permanent tooth usually from a prior infection of a nearby primary tooth. Hypoplasia may also result from antineoplastic therapy. Dental fluorosis
Dental fluorosis
Dental fluorosis is a developmental disturbance of dental enamel caused by excessive exposure to high concentrations of fluoride during tooth development. The risk of fluoride overexposure occurs between the ages of 3 months and 8 years. In its mild forms , fluorosis often appears as unnoticeable,...

 is condition which results from ingesting excessive amounts of fluoride
Fluoride
Fluoride is the anion F−, the reduced form of fluorine when as an ion and when bonded to another element. Both organofluorine compounds and inorganic fluorine containing compounds are called fluorides. Fluoride, like other halides, is a monovalent ion . Its compounds often have properties that are...

 and leads to teeth which are spotted, yellow, brown, black or sometimes pitted. Enamel hypoplasia resulting from syphilis
Syphilis
Syphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subspecies pallidum. The primary route of transmission is through sexual contact; however, it may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis...

 is frequently referred to as Hutchinson's teeth
Hutchinson's teeth
Hutchinson's teeth are a sign of congenital syphilis. Babies with this have teeth that are smaller and more widely spaced than normal and which have notches on their biting surfaces...

, which is considered one part of Hutchinson's triad
Hutchinson's triad
Hutchinson's triad is named after Sir Jonathan Hutchinson . It is a common pattern of presentation for congenital syphilis, and consists of three phenomena: interstitial keratitis, Hutchinson incisors, and eighth nerve deafness.- References :...

.

Destruction after development

Tooth destruction from processes other than dental caries
Dental caries
Dental caries, also known as tooth decay or a cavity, is an irreversible infection usually bacterial in origin that causes demineralization of the hard tissues and destruction of the organic matter of the tooth, usually by production of acid by hydrolysis of the food debris accumulated on the...

 is considered a normal physiologic process but may become severe enough to become a pathologic condition. Attrition
Attrition (dental)
Attrition is the loss of teeth structure by mechanical forces from opposing teeth. Attrition initially affects the enamel and, if unchecked, may proceed to the underlying dentin. Once past the enamel, attrition quickly destroys the softer dentin. Erosion is a very important contributing factor to...

 is the loss of tooth structure by mechanical forces from opposing teeth. Attrition initially affects the enamel and, if unchecked, may proceed to the underlying dentin. Abrasion
Abrasion (dental)
Abrasion is the loss of tooth structure by mechanical forces from a foreign element. If this force begins at the cementoenamel junction, then progression of tooth loss can be rapid since enamel is very thin in this region of the tooth...

 is the loss of tooth structure by mechanical forces from a foreign element. If this force begins at the cementoenamel junction, then progression of tooth loss can be rapid since enamel is very thin in this region of the tooth. A common source of this type of tooth wear is excessive force when using a toothbrush. Erosion
Erosion (dental)
Acid erosion, also known as dental erosion, is the irreversible loss of tooth structure due to chemical dissolution by acids not of bacterial origin. Dental erosion is the most common chronic disease of children ages 5–17, although it is only relatively recently that it has been recognised...

 is the loss of tooth structure due to chemical dissolution by acids not of bacterial origin. Signs of tooth destruction from erosion is a common characteristic in the mouths of people with bulimia since vomiting results in exposure of the teeth to gastric acids. Another important source of erosive acids are from frequent sucking of lemon juice
Lemon juice
The lemon fruit, from a citrus plant, provides a useful liquid when squeezed. Lemon juice, either in natural strength or concentrated, is sold as a bottled product, usually with the addition of preservatives and a small amount of lemon oil.-Uses:...

. Abfraction
Abfraction
Abfraction is the loss of tooth structure from flexural forces. It is hypothesized that enamel, especially at the cementoenamel junction , undergo this pattern of destruction by separating the enamel rods....

 is the loss of tooth structure from flexural forces. As teeth flex under pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...

, the arrangement of teeth touching each other, known as occlusion
Occlusion (dentistry)
Occlusion, in a dental context, means simply the contact between teeth. More technically, it is the relationship between the maxillary and mandibular teeth when they approach each other, as occurs during chewing or at rest....

, causes tension
Tension (mechanics)
In physics, tension is the magnitude of the pulling force exerted by a string, cable, chain, or similar object on another object. It is the opposite of compression. As tension is the magnitude of a force, it is measured in newtons and is always measured parallel to the string on which it applies...

 on one side of the tooth and compression on the other side of the tooth. This is believed to cause V-shaped depressions on the side under tension and C-shaped depressions on the side under compression. When tooth destruction occurs at the roots of teeth, the process is referred to as internal resorption
Internal resorption
Internal resorption is an unusual condition of a tooth when the dentin and pulpal walls begin to resorb centrally within the root canal. The first evidence of the lesion may be the appearance of a pink-hued area on the crown of the tooth; this condition is referred to as pink tooth of Mummery,...

, when caused by cells within the pulp, or external resorption
External resorption
External resorption is a condition of a tooth where the root surface is lost. This can be caused by chronic inflammation, cysts, tumors, trauma, reimplantation of a tooth, or sometimes the cause is unknown.-References:...

, when caused by cells in the periodontal ligament.

Discoloration

Discoloration of teeth may result from bacteria stains, tobacco, tea, coffee, foods with an abundance of chlorophyll
Chlorophyll
Chlorophyll is a green pigment found in almost all plants, algae, and cyanobacteria. Its name is derived from the Greek words χλωρος, chloros and φύλλον, phyllon . Chlorophyll is an extremely important biomolecule, critical in photosynthesis, which allows plants to obtain energy from light...

, restorative materials, and medications. Stains from bacteria may cause colors varying from green to black to orange. Green stains also result from foods with chlorophyll or excessive exposure to copper or nickel. Amalgam, a common dental restorative material, may turn adjacent areas of teeth black or gray. Long term use of chlorhexidine, a mouthwash may encourage extrinsic stain formation near the gingiva on teeth. This is usually easy for a hygienist to remove. Systemic disorders also can cause tooth discoloration. Congenital erythropoietic porphyria causes porphyrin
Porphyrin
Porphyrins are a group of organic compounds, many naturally occurring. One of the best-known porphyrins is heme, the pigment in red blood cells; heme is a cofactor of the protein hemoglobin. Porphyrins are heterocyclic macrocycles composed of four modified pyrrole subunits interconnected at...

s to be deposited in teeth, causing a red-brown coloration. Blue discoloration may occur with alkaptonuria
Alkaptonuria
Alkaptonuria is a rare inherited genetic disorder of phenylalanine and tyrosine metabolism. This is an autosomal recessive condition that is due to a defect in the enzyme homogentisate 1,2-dioxygenase , which participates in the degradation of tyrosine...

 and rarely with Parkinson's disease
Parkinson's disease
Parkinson's disease is a degenerative disorder of the central nervous system...

. Erythroblastosis fetalis and biliary atresia
Biliary atresia
Biliary atresia, also known as "extrahepatic ductopenia" and "progressive obliterative cholangiopathy" is a congenital or acquired disease of the liver and one of the principle forms of chronic rejection of a transplanted liver allograft. As a birth defect in newborn infants, it has an occurrence...

 are diseases which may cause teeth to appear green from the deposition of biliverdin
Biliverdin
Biliverdin is a green tetrapyrrolic bile pigment, and is a product of heme catabolism. It is the pigment responsible for a greenish color sometimes seen in bruises.- Metabolism :...

. Also, trauma may change a tooth to a pink, yellow, or dark gray color. Pink and red discolorations are also associated in patients with lepromatous leprosy
Leprosy
Leprosy or Hansen's disease is a chronic disease caused by the bacteria Mycobacterium leprae and Mycobacterium lepromatosis. Named after physician Gerhard Armauer Hansen, leprosy is primarily a granulomatous disease of the peripheral nerves and mucosa of the upper respiratory tract; skin lesions...

. Some medications, such as tetracycline antibiotics, may become incorporated into the structure of a tooth, causing intrinsic staining of the teeth.

Alteration of eruption

Tooth eruption may be altered by some environmental factors. When eruption is prematurely stopped, the tooth is said to be impacted. The most common cause of tooth impaction is lack of space in the mouth for the tooth. Other causes may be tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...

s, cyst
Cyst
A cyst is a closed sac, having a distinct membrane and division on the nearby tissue. It may contain air, fluids, or semi-solid material. A collection of pus is called an abscess, not a cyst. Once formed, a cyst could go away on its own or may have to be removed through surgery.- Locations :* Acne...

s, trauma, and thickened bone or soft tissue. Ankylosis
Ankylosis
Ankylosis or anchylosis is a stiffness of a joint due to abnormal adhesion and rigidity of the bones of the joint, which may be the result of injury or disease. The rigidity may be complete or partial and may be due to inflammation of the tendinous or muscular structures outside the joint or of...

 of a tooth occurs when the tooth has already erupted into the mouth but the cementum or dentin has fused with the alveolar bone. This may cause a person to retain their primary tooth instead of having it replaced by a permanent one.

A technique for altering the natural progression of eruption is employed by orthodontists who wish to delay or speed up the eruption of certain teeth for reasons of space maintenance or otherwise preventing crowding and/or spacing. If a primary tooth is extracted before its succeeding permanent tooth's root reaches ⅓ of its total growth, the eruption of the permanent tooth will be delayed. Conversely, if the roots of the permanent tooth are more than ⅔ complete, the eruption of the permanent tooth will be accelerated. Between ⅓ and ⅔, it is unknown exactly what will occur to the speed of eruption.

Abnormality in number

  • Anodontia
    Anodontia
    In dentistry, anodontia, also called anodontia vera, is a rare genetic disorder characterized by the congenital absence of all primary or permanent teeth. It is associated with the group of skin and nerve syndromes called the ectodermal dysplasias...

     is the total lack of tooth development.
  • Hyperdontia
    Hyperdontia
    Hyperdontia is the condition of having supernumerary teeth, or teeth which appear in addition to the regular number of teeth.-Types:Supernumerary teeth can be classified by shape and by position...

     is the presence of a higher-than-normal number of teeth.
  • Hypodontia
    Hypodontia
    In dentistry, hypodontia is the condition at which the patient has missing teeth as a result of their failure to develop. Hypodontia describes a situation where the patient is missing up to 6 teeth, excluding the 3rd molars. Missing third molars occur in 9-30% of population...

     is the lack of some teeth. Usually:
    • Hypodontia refers to the lack of development of one or more teeth
    • Oligodontia may be used to describe the absence of 6 or more teeth.

Some systemic disorders which may result in hyperdontia include Apert syndrome
Apert syndrome
Apert syndrome is a form of acrocephalosyndactyly, a congenital disorder characterized by malformations of the skull, face, hands and feet. It is classified as a branchial arch syndrome, affecting the first branchial arch, the precursor of the maxilla and mandible...

, Cleidocranial dysostosis
Cleidocranial dysostosis
Cleidocranial dysostosis, also called Cleidocranial dysplasia, is a hereditary congenital disorder due to haploinsufficiency caused by mutations in the CBFA1 gene also called Runx2, located on the short arm of chromosome 6....

, Crouzon syndrome
Crouzon syndrome
Crouzon syndrome is a genetic disorder known as a branchial arch syndrome. Specifically, this syndrome affects the first branchial arch, which is the precursor of the maxilla and mandible...

, Ehlers–Danlos syndrome, Gardner syndrome, and Sturge–Weber syndrome. Some systemic disorders which may result in hypodontia include Crouzon syndrome, Ectodermal dysplasia
Ectodermal dysplasia
Ectodermal dysplasia is not a single disorder, but a group of syndromes all deriving from abnormalities of the ectodermal structures. More than 150 different syndromes have been identified. Despite some of the syndromes having different genetic causes the symptoms are sometimes very similar...

, Ehlers–Danlos syndrome, and Gorlin syndrome.

Abnormality in size

  • Microdontia
    Microdontia
    Microdontia is a condition in which teeth appear smaller than normal. In the generalized form, all teeth are involved. In the localized form, only a few teeth are involved. The most common teeth affected are the upper lateral incisors and third molars...

     is a condition where teeth are smaller than the usual size.
  • Macrodontia
    Macrodontia (tooth)
    Macrodontia is a condition in which any tooth or teeth appear larger than normal for that particular type of tooth. True macrodontia that involves the entire dentition is rare. It is more common that there is an enlargement of a single tooth due to a disturbance of morphodifferentiation...

     is where teeth are larger than the usual size.


Microdontia of a single tooth is more likely to occur in a maxillary lateral incisor
Maxillary lateral incisor
The Maxillary lateral incisor is a tooth that is located distally from both maxillary central incisors of the mouth and mesially from both maxillary canines. As with all incisors, their function is for shearing or cutting food during mastication, commonly known as chewing. There are no cusps on...

. The second most likely tooth to have microdontia are third molars. Macrodontia of all the teeth is known to occur in pituitary gigantism
Gigantism
Gigantism, also known as giantism , is a condition characterized by excessive growth and height significantly above average...

 and pineal
Pineal gland
The pineal gland is a small endocrine gland in the vertebrate brain. It produces the serotonin derivative melatonin, a hormone that affects the modulation of wake/sleep patterns and seasonal functions...

 hyperplasia
Hyperplasia
Hyperplasia means increase in number of cells/proliferation of cells. It may result in the gross enlargement of an organ and the term is sometimes mixed with benign neoplasia/ benign tumor....

. It may also occur on one side of the face in cases of hemifacial hyperplasia.

Abnormality in shape

  • Gemination
    Tooth gemination
    The phenomenon of gemination arises when two teeth develop from one tooth bud and, as a result, the patient has an extra tooth, in contrast to fusion, where the patient would appear to be missing one tooth....

     occurs when a developing tooth incompletely splits into the formation of two teeth.
  • Fusion
    Tooth fusion
    The phenomenon of tooth fusion arises through union of two normally separated tooth germs, and depending upon the stage of development of the teeth at the time of union, it may be either complete or incomplete. On some occasions, two independent pulp chambers and root canals can be seen. However,...

     is the union of two adjacent teeth during development.
  • Concrescence
    Concrescence
    Concrescence is a condition of teeth where the cementum overlying the roots of at least two teeth join together. The cause can sometimes be attributed to trauma or crowding of teeth. tizaak Surgical separation of the teeth may be necessary if one is to be extracted....

     is the fusion of two separate teeth only in their cementum.
  • Accessory cusps
    Cusp (dentistry)
    A cusp is an occlusal or incisal eminence on a tooth.Canine teeth, otherwise known as cuspids, each possess a single cusp, while premolars, otherwise known as bicuspids, possess two each. Molars normally possess either four or five cusps...

     are additional cusps on a tooth and may manifest as a Talon cusp
    Talon cusp
    A talon cusp, also known as an "eagle's talon", is an extra cusp on an anterior tooth. The term refers to the same condition as dens evaginatus, but the talon cusp is the manifestation of dens evaginatus on anterior teeth. The incidence has been found to range from less than 1% to 6% of the...

    , Cusp of Carabelli
    Cusp of Carabelli
    The cusp of Carabelli, or Carabelli's tubercle, or tuberculum anomale of Georg Carabelli is a small additional cusp at the mesiopalatal line angle of maxillary first molars. This extra cusp is usually found on the first molar, and becomes progressively less likely in the second, third molars...

    , or Dens evaginatus
    Dens evaginatus
    Dens evaginatus is a condition found in teeth where the outer surface appears to form an extra bump or cusp. Premolars are more likely to be affected than any other tooth. This may be seen more frequently in Asians. The pulp of the tooth may extend into the dens evaginatus. There is a risk of the...

    .
  • Dens invaginatus
    Dens invaginatus
    Dens invaginatus, also known as dens in dent, "Tooth within a tooth" is a condition found in teeth where the outer surface folds inward...

    , also called Dens in dente, is a deep invagination in a tooth causing the appearance of a tooth within a tooth.
  • Ectopic enamel
    Ectopic enamel
    Ectopic enamel is an abnormality with shape of teeth. It is when tooth enamel is found in an unusual location, such as at the root of a tooth....

     is enamel found in an unusual location, such as the root of a tooth.
  • Taurodontism
    Taurodontism
    Taurodontism is a condition found in molar teeth where the body of the tooth and pulp chamber is enlarged vertically at the expense of the roots. As a result, the floor of the pulp and the furcation of the tooth is moved apically down the root...

     is a condition where the body of the tooth and pulp chamber is enlarged, and is associated with Klinefelter syndrome, Tricho-dento-osseous syndrome, Triple X syndrome
    Triple X syndrome
    Triple X syndrome is a form of chromosomal variation characterized by the presence of an extra X chromosome in each cell of a human female. The condition always produces females, with an XX pair of chromosomes, as well as an additional chromosome, resulting in the formation of XXX. A mosaic form...

    , and XYY syndrome
    XYY syndrome
    XYY syndrome is an aneuploidy of the sex chromosomes in which a human male receives an extra Y-chromosome, giving a total of 47 chromosomes instead of the more usual 46. This produces a 47,XYY karyotype...

    .
  • Hypercementosis
    Hypercementosis
    Etiology of Hypercementosis can be caused by many things. A way to remember the causes is "PIG ON TAP" -PagetsIdiopathicGigantismOccusal TraumaNon functional toothTraumaAcromegliaPeriapical granuloma...

     is excessive formation of cementum, which may result from trauma, inflammation, acromegaly
    Acromegaly
    Acromegaly is a syndrome that results when the anterior pituitary gland produces excess growth hormone after epiphyseal plate closure at puberty...

    , rheumatic fever
    Rheumatic fever
    Rheumatic fever is an inflammatory disease that occurs following a Streptococcus pyogenes infection, such as strep throat or scarlet fever. Believed to be caused by antibody cross-reactivity that can involve the heart, joints, skin, and brain, the illness typically develops two to three weeks after...

    , and Paget's disease of bone
    Paget's disease of bone
    Paget's disease is a chronic disorder that can result in enlarged and misshapen bones. The excessive breakdown and formation of bone tissue causes affected bone to weaken, resulting in pain, misshapen bones, fractures, and arthritis in the joints near the affected bones...

    .
  • A dilaceration
    Dilaceration
    Dilaceration is a developmental disturbance in shape of teeth. It refers to an angulation, or a sharp bend or curve, in the root or crown of a formed tooth.-Description:The condition is thought to be due to trauma during the period in which tooth is forming...

     is a bend in the root which may have been caused by trauma to the tooth during formation.
  • Supernumerary roots
    Supernumerary roots
    Supernumerary roots is a condition found in teeth there may be a larger number of roots than expected. The most common teeth affected are mandibular canines, premolars, and molars, especially third molars. Canines and most premolars, except for maxillary first premolars, usually have one root. ...

     is the presence of a greater number of roots on a tooth than expected.

Abnormality in structure

  • Amelogenesis imperfecta
    Amelogenesis imperfecta
    Amelogenesis imperfecta presents with abnormal formation of the enamel or external layer of teeth. Enamel is composed mostly of mineral, that is formed and regulated by the proteins in it...

     is a condition in which enamel does not form properly or at all.
  • Dentinogenesis imperfecta
    Dentinogenesis imperfecta
    Dentinogenesis imperfecta is a genetic disorder of tooth development. This condition causes teeth to be discolored and translucent. Teeth are also weaker than normal, making them prone to rapid wear, breakage, and loss. These problems can affect both primary teeth and permanent teeth...

     is a condition in which dentin does not form properly and is sometimes associated with osteogenesis imperfecta
    Osteogenesis imperfecta
    Osteogenesis imperfecta is a genetic bone disorder. People with OI are born with defective connective tissue, or without the ability to make it, usually because of a deficiency of Type-I collagen...

    .
  • Dentin dysplasia
    Dentin dysplasia
    Dentin dysplasia is a genetic disorder of teeth, commonly exhibiting an autosomal dominant inheritance. It is characterized by presence of normal enamel but atypical dentin with abnormal pulpal morphology. There are two types. Type I is the radicular type, and type II is the coronal type...

     is a disorder in which the roots and pulp of teeth may be affected.
  • Regional odontodysplasia
    Regional odontodysplasia
    Regional odontodysplasia is an uncommon developmental abnormality of teeth, usually localized to a certain area and nonhereditary. No predilection for race, but females are more likely to get regional odontodysplasia...

     is a disorder affecting enamel, dentin, and pulp and causes the teeth to appear "ghostly" on radiographs.

Fossil record

Because teeth are very resistant, often preserved when bones are not, and reflect the diet of the host organism, they are very valuable to archaeologists and paleontologists. Early fish such as the thelodonts had teeth for scales, suggesting that the origin of teeth was scales which were retained in the mouth. Fish as early as the late Cambrian
Cambrian
The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...

 had dentin in their exoskeleton, which may have functioned in defense or for sensing their environment. Dentin can be as hard as the rest of teeth, and is composed of collagen fibres, reinforced with hydroxyapatite.

Decalcification removes the enamel from teeth and leaves only the organic interior intact, which comprises dentin and cementine. Enamel is quickly decalcified in acids, perhaps by dissolution by plant acids or via diagenetic solutions, or in the stomachs of vertebrate predators. Enamel can be lost by abrasion or spalling, and is lost before dentin or bone are destroyed by the fossilisation process. In such a case, the 'skeleton' of the teeth would consist of the dentin, with a hollow pulp cavity.
The organic part of dentin, conversely, is destroyed by alkalis.

See also

  • Barodontalgia
    Barodontalgia
    Barodontalgia, commonly known as tooth squeeze and previously known as aerodontalgia, is a pain in tooth caused by a change in atmospheric pressure...

  • Braces
  • Dental auxiliary
    • Dental assistant
      Dental assistant
      Dental assistants assist the dental operator provide more efficient dental treatment, by preparing the patient for treatment, sterilizing instruments, passing instruments during the procedure, holding a suction device, exposing dental radiographs, taking impressions, and fabricating provisional...

    • Dental hygienist
      Dental hygienist
      thumb|right|300px|Dental hygienist holding a scalerA dental hygienist is a licensed dental professional who specializes in preventive oral health, typically focusing on techniques in oral hygiene. Local dental regulations determine the scope of practice of dental hygienists...

    • Dental technician
      Dental technician
      A dental technologist is a member of the dental team who, upon presciption from a dental clinician, constructs custom made restorative and dental appliances.There are four major disciplines within dental technology...

  • Dental notation
    Dental notation
    Dentists, in writing or speech, use several different dental notation systems for associating information to a specific tooth. The three most common systems are the FDI World Dental Federation notation, Universal numbering system , and Palmer notation method...

  • Dental tourism
    Dental tourism
    Dental tourism is a subset of the sector known as medical tourism. It involves individuals seeking dental care outside of their local healthcare systems and may be accompanied by a vacation.- Reasons for travel :...

  • Dentistry
    Dentistry
    Dentistry is the branch of medicine that is involved in the study, diagnosis, prevention, and treatment of diseases, disorders and conditions of the oral cavity, maxillofacial area and the adjacent and associated structures and their impact on the human body. Dentistry is widely considered...

  • Dragon's teeth (mythology)
    Dragon's teeth (mythology)
    In Greek myth, dragon's teeth feature prominently in the legends of the Phoenician prince Cadmus and Jason's quest for the Golden Fleece. In each case, the dragon's teeth, once planted, would grow into fully armed warriors....

  • Head and neck anatomy
    Head and neck anatomy
    Head and neck anatomy focuses on the structures of the head and neck of the human body, including the brain, bones, muscles, blood vessels, nerves, glands, nose, mouth, teeth, tongue, and throat...

  • Language
    Language
    Language may refer either to the specifically human capacity for acquiring and using complex systems of communication, or to a specific instance of such a system of complex communication...

  • Tooth fairy
    Tooth fairy
    The tooth fairy is a fantasy figure of early childhood. The folklore states that when a child loses a baby tooth, if he or she places it beneath the bed pillow, the tooth fairy will visit while the child sleeps, replacing the lost tooth with a small payment....

  • Tooth painting
    Tooth painting
    Tooth painting is an ancient custom of many countries in the Far East, such as Japan, southern China, Vietnam and Malaysia. Each region has its distinct traditions and methods....

  • Vocal tract
    Vocal tract
    The vocal tract is the cavity in human beings and in animals where sound that is produced at the sound source is filtered....


Sources

  • Ash, Major M. and Stanley J. Nelson, 2003. Wheeler’s Dental Anatomy, Physiology, and Occlusion. 8th edition. ISBN 0-7216-9382-2.
  • Cate, A.R. Ten. (1998) Oral Histology: development, structure, and function. 5th ed.
  • Neville, B.W., D. Damm, C. Allen, J. Bouquot, 2002. Oral & Maxillofacial Pathology. Second edition. ISBN 0-7216-9003-3.


External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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