Incisor

Incisor
Permanent teeth of right half of lower dental arch, seen from above.
The permanent teeth, viewed from the right.
Latin	dentes incisivi
Gray's	subject #242 1115
MeSH	Incisor

Incisors (from Latin incidere, "to cut") are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.

Function

In many omnivorous mammals, such as the human, they are adapted for shearing sharply. 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, just as is the case with Narwhals, where normally one of them develops into a straight and twisted tusk. The incisors of rodents grow throughout life and are worn by gnawing.

Number and types of incisors

In humans

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

• maxillary central incisor (upper jaw, closest to the center of the lips)
• maxillary lateral incisor (upper jaw, beside the maxillary central incisor)
• mandibular central incisor (lower jaw, closest to the center of the lips)
• mandibular lateral incisor (lower jaw, beside the mandibular central incisor)

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.

In non-human animals

Among other animals, some other primates, cats and horses have twelve. Rodents have four, while Foxes have nine. Rabbits and hares (lagomorphs) were once considered rodents, but are distinguished by having eight—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.

Additional images

• 

  Mouth (oral cavity)

• 

  Left maxilla. Outer surface.

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  Base of skull. Inferior surface.

See also

• canine tooth
• premolar
• molar
• Shovel-shaped incisors