teeth

The teeth (singular: tooth; collective term: dentition) can be both primary and secondary, with the eruption of permanent teeth occurring over a long period between the ages of 6 and 24 years. When an individual has a complete set of teeth, they are said to be dentate, if some are missing they are partially dentate. Complete absence of the teeth is termed edentulism, if only a few teeth are remaining then partial edentulism.

Gross anatomy

There are twenty deciduous (primary) teeth in young children, with ten per jaw and five in each quadrant, which consist of (distal to mesial):

• two molars
• one canine
• two incisors
  • central incisors are the first to erupt, around 6 months of age

The deciduous (primary) teeth start erupting at six months (lower central incisor) and are completely erupted by around 3 years of age. They are then progressively replaced by permanent (secondary) teeth from the age of six with the final eruption of the third molar between 18-24 years .

There are normally a total of 32 permanent (secondary) teeth in adults, with 16 per jaw and eight in each quadrant, which consists of (distal to mesial) :

• three molars
  • "wisdom teeth" refer to the third molars
• two premolars
• one canine
• two incisors

The dental arch describes the crescentic formation of teeth on each jaw.

Morphology

The tooth sits in alveolar processes of the upper jaw (maxilla) or lower jaw (mandible). Each tooth is mainly composed of dentin and is made up of several parts :

• crown: portion of the tooth projecting out of bone
  • dentin is covered by enamel
• root: portion of tooth embedded in bone
  • composed of cementum
• pulp chamber and root canal: lie centrally within the tooth and contain neurovascular structures
• apical foramen: lies at the apex of the tooth root

The periodontal ligament connects the tooth root to the underlying lamina dura, which itself is the cortical bone which lines the tooth socket. This joint between a tooth and alveolar bone is a fibrous joint called a gomphosis or dental-alveolar joint.

Arterial supply

Arterial supply to the teeth is derived from the maxillary artery, a branch of the external carotid artery, via the:

• superior alveolar arteries
  • posterior superior alveolar artery: branch of the maxillary artery in the pterygopalatine fossa
  • middle superior alveolar artery: small branch of the infraorbital artery
  • anterior superior alveolar artery: branch of the infraorbital artery
• inferior alveolar artery: arises from the maxillary artery then enters the mandibular foramen

Venous drainage

Venous drainage of the teeth is into either the:

• pterygoid venous plexus, or​
• facial vein

via vessels that generally follow the arteries

Lymphatic drainage

The teeth do not have any lymphatic vessels.

Innervation

• the maxillary teeth are supplied by a group of superior alveolar branches of the infraorbital nerve, from the maxillary division of the trigeminal nerve:
  • posterior superior alveolar nerve supplies the maxillary molar teeth apart from the mesiobuccal root of the first maxillary molar
  • middle superior alveolar nerve supplies the mesiobuccal root of the first maxillary molar and premolars
  • anterior superior alveolar nerve supplies the incisors and canines
• the mandibular teeth are supplied by the inferior alveolar nerve: branch of the mandibular division of the trigeminal nerve:
  • small twigs of the inferior alveolar nerve whilst in the mandibular canal supplies the molars and premolars
  • the incisive nerve, a terminal branch of the inferior alveolar nerve supplies the canines and incisors

Variant anatomy

• hyperdontia: supernumerary teeth
• hypodontia: congenital absence of teeth
• macrodontia: atypically large teeth
• microdontia: atypically small teeth

Radiographic appearance

Plain radiograph/OPG/CT

The teeth are well visualized on these modalities :

• enamel: most radiopaque part, hardest tissue in the human body
• dentin and cementum are less radiopaque than the enamel and are indistinguishable on these modalities
• pulp chamber and root canal are lucent and positioned centrally
• periodontal ligament is a linear lucency between the tooth and the lamina dura

Related pathology

• edentulism
• dental (periapical) abscess
• dental caries
• periapical cyst
• periapical granuloma
• meth mouth
• dentigerous cyst

See also

• dental terminology
• Fédération Dentaire Internationale (FDI) notation
• American Dental Association (ADA) Universal Numbering System

Siehe auch:

• überzählige Zähne
• Zahnschema
• Röntgenstatus
• Malformationen der Zähne
• Weisheitszahn
• Milchzähne
• Zahnimplantate
• Backenzahn
• Zahnformel

und weiter:

• Foramen apicale