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Canine tooth
Long, pointed tooth in mammals From Wikipedia, the free encyclopedia
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A canine tooth, also called a cuspid or eye tooth, is a pointed tooth located between the incisors and premolars. Most mammals, including humans, have four canines—one in each quadrant of the mouth. Their primary function is to grip and tear food, though in some species they are also used for display or defense. In humans, the upper canines (maxillary) are usually more prominent than the lower ones (mandibular). When reduced or flattened, canines may resemble incisors, in which case they are described as incisiform. In animals such as dogs, the canines are especially pronounced, giving the group its name.
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In adult humans, there are four permanent canines: two in the upper jaw (maxillary canines) and two in the lower jaw (mandibular canines). Each is positioned at the corners of the dental arch, next to the lateral incisors and in front of the first premolars. Canines are classified as anterior teeth, along with the incisors.
Anatomically, the surfaces of a canine are described using standard dental terms. The side closest to the midline of the face is the mesial surface, while the side farthest from the midline is the distal surface. The side facing the cheek is called buccal (or labial in the case of incisors and canines), and the side facing the tongue is lingual.
Eruption
In humans, the upper canine teeth (often called eye teeth because of their position beneath the eyes[1]) are usually larger and longer than the lower canines, and they often have a noticeable basal ridge. The upper canines typically erupt between ages 11 and 12, while the lower canines emerge earlier, between ages 9 and 10. The upper deciduous (baby) canines usually appear between 16 and 22 months of age and are shed between ages 10 and 12. The lower deciduous canines erupt between 17 and 22 months and are shed slightly earlier, between ages 9 and 12.[2]
Developmental defects
A common developmental defect involving the canines is transposition, where two adjacent teeth switch places. This occurs most often with the permanent maxillary (upper) canine, which may switch positions with the first premolar. In the mandible (lower jaw), the canine may transpose with the lateral incisor. In some cases, canines may also be congenitally absent.[3][4]
Maxillary canine morphology
From the front (facial view), maxillary canines are about one millimetre narrower than the central incisors. Their mesial (closer to the midline) surfaces resemble the lateral incisors, while their distal (away from the midline) surfaces resemble the first premolars. They tend to be slightly darker and more yellow than other front teeth. From the lingual (tongue-side) view, they show strong mesial and distal marginal ridges, along with a well-developed cingulum. A prominent lingual ridge divides the surface in two, creating mesial and distal fossae. Viewed from the side (proximal view), maxillary canines resemble incisors but appear more robust, especially near the cingulum. From above (incisal view), the tooth looks asymmetrical: the mesial edge is slightly shorter than the distal edge, which places the cusp tip closer to the midline. Maxillary canines are thicker labiolingually (front to back) than mesiodistally (side to side). The contact points between adjacent teeth are also uneven: on the mesial side, the contact is near the junction of the incisal and middle thirds of the crown, while on the distal side it is more cervical, in the middle of the middle third. The root of the maxillary canine is the longest of any human tooth and has a conical shape.[5]
Mandibular canine morphology
The lower canines lie closer to the midline than the upper canines, so their cusps align with the spaces between the maxillary canine and lateral incisor. From the facial (labial) aspect, the mandibular canine is distinctly narrower mesiodistally than the maxillary canine. Its root is compressed mesiodistally, shows marked longitudinal grooves on both sides, and may be as long as the maxillary root; in some cases it is bifurcated. A characteristic feature is the comparatively straight labial profile (the maxillary canine is more curved). As with the maxillary canine, the mesial incisal edge (cusp ridge) is shorter than the distal, and the cusp tip is displaced slightly lingually relative to that of the maxillary canine.
On the lingual surface, the mandibular canine is smoother than the maxillary canine and has a less prominent cingulum. With attrition, the cusp may blunt and the crown can resemble a maxillary lateral incisor.[5]
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Sexual dimorphism
In many mammals, canines in one or both jaws are much larger in males than in females and in some female individuals are small or absent. Examples include antelopes, musk-deer, camels, horses, wild boar, several apes, seals, narwhal, and walrus.[6] Male dogs typically have larger canines with a different contour than females.[7]
Among anthropoids, human males have comparatively small canines and show little sexual dimorphism in canine size. Some researchers propose that canine reduction in human males reflects selection for reduced male aggression and less reliance on canine display. Sexual dimorphism in canine size is also relatively slight in bonobos and chimpanzees.[8][9]
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Non-synapsids
In non-synapsids, such as reptiles and crocodiles, teeth similar to canines may be termed "caniniform" ("canine-shaped") teeth. Teeth or appendages with similar appearances found in many snakes and invertebrates, such as spiders, are referred to as fangs, but are usually modified to inject venom.[10]
Additional images
Medical animation showing Canine teeth and their arrangement in the mouth of an adult human being.
Mouth (oral cavity)
Left maxilla. Outer surface.
Base of skull. Inferior surface.
Unerupted permanent teeth underlie the deciduous teeth.
See also
References
External links
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