Teeth

Dr Henry Knipe et al.

Teeth can be both primary and secondary, with the eruption of permanent teeth occurring over a long period between the ages of 6 and 24. 

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 5.

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) 3

  • three molars
    • "wisdom teeth" refer to the third molars
  • two pre-molars
  • one canine
  • two incisors
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 1-3:

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

Venous drainage of the teeth is into either the pterygoid venous plexus or facial vein via vessels that generally follow the arteries.

  • hyperdontia: supernumerary teeth
  • hypodontia: congenital absence of teeth
  • macrodontia: atypically large teeth
  • microdontia: atypically small teeth
Plain radiograph / OPG / CT

The teeth are well visualised on these modalities 1-3:

  • enamel: most radiopaque part, hardest tissue in the human body
  • dentin and cemuntum 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
Head and neck anatomy
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Article information

rID: 29678
System: Head & Neck
Section: Anatomy
Tag: dental
Synonyms or Alternate Spellings:
  • Tooth
  • Tooth anatomy
  • Teeth anatomy
  • Dental anatomy
  • wisdom teeth

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Cases and figures

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    Figure 1
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    Case 1: normal permanent dentition
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    Figure 2
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    Case 2: normal primary dentition
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    Figure 3: dental notation
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    Case 3: supernumerary teeth
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    Figure 4: dental notation
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