The Anatomy, Physiology and Morphology of Teeth

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The Anatomy, Physiology and Morphology of Teeth

• By Dr. Juliana Mathews

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Tooth Anatomy

• The crown
• consists of enamel, dentine and pulp
• The root
• has a root canal with blood vessels and nerves
• covered by cementum and held together by
  periodontal fibres
• embedded in the alveolar bone
• Enamel
• white hard covering over the crown of the tooth
• no nerve or blood supply
• cannot heal or repair like bone or dentine
• Dentine
• covered by enamel on the crown and cementum on
  the roots
• protects the pulp

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Tooth Anatomy continued

• Pulp
• Consists of nerves, blood vessels and connective
  tissue
• Found in pulp chamber and root canal
• Anastomoses between venules and arterioles
• Cementum
• Covers the dentine of the root
• Attached to the periodontal ligament
• No nerve supply

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Tooth Anatomy continued

• Periodontium
• Alveolar process bony extensions of the maxilla
  and mandible that support teeth
• Cortical Plate dense outer layer of bone
  covering the spongy (cancellous) bone
• Periodontal ligament
• Periodontal fibres attach the roots to the
  alveolar bone
• has a nerve and blood supply
• provides an elastic cushion between the tooth and
  bone
• Gingiva covers the teeth and the alveolar
  process
• 
  

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Root Canal System

• Pulp chamber is found on the coronal part of the
  tooth
• Reduces in size with age due to secondary dentine
  due to physiological or pathological reasons
• Orifices to the root canal are found on the floor
  of the pulp chamber
• Canals taper towards the apex
• The narrowest part of the canal is found at the
  apical constriction, which opens out as the
  apical foramen and exists to one side i.e.
  0.5mm-1mm from the anatomical apex
• New layers of cementum are constantly being laid
  down, therefore the centre of the foramina
  deviates from the apical centre
• Lateral canals can develop between the main body
  of the root canal and the periodontal ligament
  space
• Accessory canals can develop in the apical region
  forming the apical delta
• Lateral and Accessory canals develop due to a
  break in the Hertwigs epithelial root sheath or
  during the development, the sheath grows around
  the existing blood vessel
• Lateral canals can be impossible to instrument
  and can compromise obturation

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Root canal system continued

• Some roots can have more than one canal and they
  dont always merge
• Single rooted teeth that have a single canal can
  end in a single foramen. Some have an apical
  delta and have a single canal but many exits
• Multi- rooted teeth commonly have multiple
  foramina and each root can have two or three
  canals. Some canals merge before their exit and
  some can leave the root independently
• Eg. Some maxillary second premolars can have two
  roots (usually are single rooted) or a single
  root with 2 canals
• Eg. The mesio-buccal root of the maxillary first
  molar can have two canals (usually one canal
  present)

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The complexity of the root canal
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Physiology of the Dental Pulp

• Nerve fibres
• consist of sensory (afferent) fibres, sympathetic
  fibres and parasympathetic fibres
• sensory fibres pass through the apical foramen
  and end at the peripheral pulp
• sensory nerve fibres originate from the
  trigeminal ganglion
• C fibres
• Unmyelinated, high threshold fibres responding to
  mechanical, thermal or chemical stimulation
• Dull, poor localized pain
• A- delta fibres
• myelinated, low threshold mechano- receptors
• sharp localized pain
• A-beta fibres

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Pain

• Inflammation of pulp develops
• Increased pulpal pressure against the sensory
  nerve endings
• Sensitized nerves release neuropeptides and cause
  inflammation Neurogenic inflammation
• A-delta fibres respond to hydrodynamic stimuli
• C-fibres respond to the inflammatory mediators
• Pheripheral sensory nerves produce pain
  hyperalgesia
• Peripheral sensory nerves sprout/branch in the
  inflammed area but disappear as the inflammation
  subside
• Central sensitization occurs when there is a flow
  of continuous pain impulses which can occur in
  acute and chronic states

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The Innervation of Teeth

• Trigeminal Nerve (CN V)
• Three sensory branches
• Opthalmic branch supplies the orbit and forehead
• Maxillary branch supplies the maxillary sinus and
  upper jaw teeth
• Mandibular branch supplies the tongue and the
  lower jaw teeth
• Facial Nerve (CN VII)
• Motor and sensory branches
• Innervates
• muscles of facial expression
• taste buds of the anterior 2/3 of the tongue
• salivary glands

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Innervation of Teeth continued

• Maxillary Teeth
• Anterior superior alveolar nerve upper incisors
  and canines (CNV2)
• Middle superior alveolar nerve upper premolars
  and the mesio-buccal root of the maxillary first
  molar (CNV2)
• Posterior superior alveolar nerve upper molars
  except the mesio-buccal root of the maxillary
  first molar (CNV2)
• Mandibular Teeth
• Inferior alveolar nerve mandibular teeth,
  gingiva and lower lip unilaterally (CNV3)
• Lingual nerve anterior 2/3 of tongue and mucosa
  of the floor of the mouth (CNV3)
• Buccal nerve gingiva on the buccal side of
  posterior teeth (CNV3)

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The Branches of the Trigeminal Nerve
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Blood supply

• Maxillary teeth
• Superior alveolar artery anterior, middle and
  posterior branch (Maxillary Artery)
• Mandibular teeth
• Inferior alveolar artery (Maxillary Artery)

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Tooth Morphology

• Please look the additional notes for this
  section

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ANY QUESTIONS