Teeth

At a glance

English

Teeth

Latin (TA2)

Dentes

System

Bone

Region

Head

In order

From the upper medial incisor to the lower second molar tooth

About the teeth

The permanent teeth sit in sockets in the alveolar processes of the maxilla above and the mandible below, forming an upper and a lower dental arch. Each half-arch, or quadrant, follows the same sequence from the midline backwards: two incisors, one canine, two premolars and then the molars. The model shows the first and second molars in each quadrant; a third molar, the wisdom tooth, may erupt behind them in early adulthood or stay buried in the bone. Each tooth is held in its socket by the periodontal ligament, a fibrous joint called a gomphosis.

Every tooth has a crown covered in enamel, the hardest tissue in the body, and one or more roots covered in cementum, meeting at the neck along the gum line. Beneath the enamel lies dentine, and in the centre a pulp cavity holds the nerves and vessels, which enter through a small opening at the tip of each root. Surfaces are described by direction: mesial towards the midline of the arch, distal away from it, labial or buccal towards the lips and cheeks, lingual or palatal towards the tongue and palate, and occlusal or incisal where the teeth meet.

Shape changes along the arch to match the job. The incisors at the front have thin, chisel-like edges for biting through food. The canines are the longest teeth, with a single pointed cusp and a deep root that raises a ridge on the jaw; no tooth has a longer root than the upper canine. The premolars, or bicuspids, are transitional teeth with a large buccal cusp and a smaller lingual one, handing food on towards the molars for grinding. The molars are the broadest, with four or five cusps on a wide grinding table: the upper ones usually have three roots, two on the cheek side and one on the palate side, and the lower ones two, front and back.

Children have a first, deciduous set without premolars, and the permanent teeth begin to come through at about six years of age, the first molars and lower central incisors leading. Upper teeth are supplied by the superior alveolar nerves from the maxillary nerve and lower teeth by the inferior alveolar nerve from the mandibular nerve, both branches of the trigeminal; the alveolar branches of the maxillary artery provide the blood. Dental decay, gum disease and the roots of upper molars that reach close to the maxillary sinus all follow from this arrangement.