Incisor

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Incisor
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Permanent teeth of the right half of the lower dental arch, seen from above.
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The permanent teeth of a human, viewed from the right.
Details
Identifiers
Latin dens incisivus
MeSH D007180
TA98 A05.1.03.004
TA2 906
FMA 12823
Anatomical terminology

Incisors (from Latin incidere, "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, whereas armadillos have none. [1]

Contents

Structure

Adult humans normally have eight incisors, two of each type. The types of incisors are:

Children with a full set of deciduous teeth (primary teeth) also have eight incisors, named the same way as in permanent teeth. Young children may have from zero to eight incisors depending on the stage of their tooth eruption and tooth development. Typically, the mandibular central incisors erupt first, followed by the maxillary central incisors, the mandibular lateral incisors and finally the maxillary laterals. The rest of the primary dentition erupts after the incisors. [2]

Apart from the first molars, the incisors are also the first permanent teeth to erupt, following the same order as the primary teeth, among themselves.

Other animals

Among other animals, the number varies from species to species. Opossums have 18, whereas armadillos have none. Cats, dogs, foxes, pigs, and horses have twelve. Rodents have four. Rabbits and hares (lagomorphs) were once considered rodents, but are distinguished by having six—one small pair, called "peg teeth", is located directly behind the most anterior pair. Incisors are used to bite off tough foods, such as red meat.

Cattle (cows, bulls, etc.) have none on top but a total of six on the bottom.

Function

In cats, the incisors are small; biting off meat is done with the canines and the carnassials. In elephants, the upper incisors are modified into curved tusks (unlike with Narwhals, where it is a canine that develops into a straight and twisted tusk). [3] The incisors of rodents grow throughout life and are worn by gnawing. In humans, the incisors serve to cut off pieces of food, as well as in the grip of other food items.

Additional images

See also

Related Research Articles

<span class="mw-page-title-main">Human tooth</span> Calcified whitish structure in humans mouths used to break down food

Human teeth function to mechanically break down items of food by cutting and crushing them in preparation for swallowing and digesting. As such, they are considered part of the human digestive system. Humans have four types of teeth: incisors, canines, premolars, and molars, which each have a specific function. The incisors cut the food, the canines tear the food and the molars and premolars crush the food. The roots of teeth are embedded in the maxilla or the mandible and are covered by gums. Teeth are made of multiple tissues of varying density and hardness.

<span class="mw-page-title-main">Dentition</span> Development and arrangement of teeth

Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, it is the characteristic arrangement, kind, and number of teeth in a given species at a given age. That is, the number, type, and morpho-physiology of the teeth of an animal.

<span class="mw-page-title-main">Canine tooth</span> Long pointed tooth in mammals

In mammalian oral anatomy, the canine teeth, also called cuspids, dog teeth, eye teeth, vampire teeth, or vampire fangs, are the relatively long, pointed teeth. In the context of the upper jaw, they are also known as fangs. They can appear more flattened however, causing them to resemble incisors and leading them to be called incisiform. They developed and are used primarily for firmly holding food in order to tear it apart, and occasionally as weapons. They are often the largest teeth in a mammal's mouth. Individuals of most species that develop them normally have four, two in the upper jaw and two in the lower, separated within each jaw by incisors; humans and dogs are examples. In most species, canines are the anterior-most teeth in the maxillary bone. The four canines in humans are the two upper maxillary canines and the two lower mandibular canines. They are specially prominent in dogs (Canidae), hence the name.

Hypodontia is defined as the developmental absence of one or more teeth excluding the third molars. It is one of the most common dental anomalies, and can have a negative impact on function, and also appearance. It rarely occurs in primary teeth and the most commonly affected are the adult second premolars and the upper lateral incisors. It usually occurs as part of a syndrome that involves other abnormalities and requires multidisciplinary treatment.

<span class="mw-page-title-main">Malocclusion</span> Medical condition

In orthodontics, a malocclusion is a misalignment or incorrect relation between the teeth of the upper and lower dental arches when they approach each other as the jaws close. The English-language term dates from 1864; Edward Angle (1855-1930), the "father of modern orthodontics", popularised it. The word "malocclusion" derives from occlusion, and refers to the manner in which opposing teeth meet.

<span class="mw-page-title-main">Maxillary central incisor</span> Tooth

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 (chewing). There is typically a single cusp on each tooth, called an incisal ridge or incisal edge. Formation of these teeth begins at 14 weeks in utero for the deciduous (baby) set and 3–4 months of age for the permanent set.

<span class="mw-page-title-main">Maxillary lateral incisor</span>

The maxillary lateral incisors are a pair of upper (maxillary) teeth that are located laterally from both maxillary central incisors of the mouth and medially from both maxillary canines. As with all incisors, their function is for shearing or cutting food during mastication, commonly known as chewing. There are generally no cusps on the teeth, but the rare condition known as talon cusps are most prevalent on the maxillary lateral incisors. The surface area of the tooth used in eating is called an incisal ridge or incisal edge. Though relatively the same, there are some minor differences between the deciduous (baby) maxillary lateral incisor and that of the permanent maxillary lateral incisor. The maxillary lateral incisors occlude in opposition to the mandibular lateral incisors.

<span class="mw-page-title-main">Maxillary canine</span>

In human dentistry, the maxillary canine is the tooth located laterally from both maxillary lateral incisors of the mouth but mesial from both maxillary first premolars. Both the maxillary and mandibular canines are called the "cornerstone" of the mouth because they are all located three teeth away from the midline, and separate the premolars from the incisors. The location of the canines reflects their dual function as they complement both the premolars and incisors during mastication, commonly known as chewing. Nonetheless, the most common action of the canines is tearing of food. The canines often erupt in the upper gums several millimeters above the gum line. The canine teeth are able to withstand the tremendous lateral pressure caused by chewing. There is a single cusp on canines, and they resemble the prehensile teeth found in carnivorous animals such as the extinct saber-toothed cat. Though relatively the same, there are some minor differences between the deciduous (baby) maxillary canine and that of the permanent maxillary canine.

<span class="mw-page-title-main">Permanent teeth</span> Second set of teeth in diphyodont mammals

Permanent teeth or adult teeth are the second set of teeth formed in diphyodont mammals. In humans and old world simians, 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.

<span class="mw-page-title-main">Mandibular canine</span>

The mandibular canine is the tooth located distally from both mandibular lateral incisors of the mouth but mesially from both mandibular first premolars. Both the maxillary and mandibular canines are called the "cornerstone" of the mouth because they are all located three teeth away from the midline, and separate the premolars from the incisors. The location of the canines reflect their dual function as they complement both the premolars and incisors during mastication, commonly known as chewing. Nonetheless, the most common action of the canines is tearing of food. The canine teeth are able to withstand the tremendous lateral pressures from chewing. There is a single cusp on canines, and they resemble the prehensile teeth found in carnivorous animals. Though relatively the same, there are some minor differences between the deciduous (baby) mandibular canine and that of the permanent mandibular canine.

<span class="mw-page-title-main">FDI World Dental Federation notation</span> Worlds most commonly used dental notation

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<span class="mw-page-title-main">Dental arch</span> Arrangement and alignment of teeth

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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 the teeth's eventual morphology is dictated during this time. Dental anatomy is also a taxonomical science: it is concerned with the naming of teeth and the structures of which they are made, this information serving a practical purpose in dental treatment.

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<span class="mw-page-title-main">Mammal tooth</span> Details of teeth found in many warm-blooded vertebrate animals

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References

  1. "Archives". dentalcare.com. Archived from the original on 29 April 2018. Retrieved 29 April 2018.
  2. Scheid, RC. (2012). Woelfel's dental anatomy (8 ed.). Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins.
  3. Nweeia, Martin; Eichmiller, Frederick C.; Hauschka, Peter V.; Tyler, Ethan; Mead, James G.; Potter, Charles W.; Angnatsiak, David P.; Richard, Pierre R.; et al. (30 March 2012). "Vestigial Tooth Anatomy and Tusk Nomenclature for Monodon Monoceros". The Anatomical Record. 295 (6): 1006–1016. doi:10.1002/ar.22449. PMID   22467529.