Incisors (from Latinincidere, "to cut") are the frontteeth present in mostmammals. They are located in thepremaxilla above and on themandible below. Humans have a total of eight (two on each side, top and bottom).Opossums have 18, whereasarmadillos,anteaters and other animals in the superorderXenarthra have none.[1]
Children with a full set ofdeciduous teeth (primary teeth) also have eight incisors, named the same way as inpermanent teeth. Young children may have from zero to eight incisors depending on the stage of theirtooth eruption andtooth 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 thefirst molars, the incisors are also the first permanent teeth to erupt, following the same order as the primary teeth, among themselves.
Among other animals, the number varies from species to species.Opossums have 18, whereasarmadillos 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.
Incats, the incisors are small; biting off meat is done with thecanines and thecarnassials. Inelephants, the upper incisors are modified into curvedtusks (unlike withnarwhals, where it is a canine that develops into a straight and twisted tusk).[3] The incisors ofrodents 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.
^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.PMID22467529.
