Transcript The Anatomy, Physiology and Morphology of the Tooth

By Dr. Juliana Mathews
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
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
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
Periodontal
Ligaments
Enamel
Dentine
Dentinal Tubules
Cementum
Pulp
Alveolar
Process
Cortical Plate
Spongy Bone
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
Root canal system continued
 Some roots can have more than one canal and they don’t 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)
The complexity of
the root canal
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

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
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
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)
The Branches of the
Trigeminal Nerve
Blood supply
 Maxillary teeth:
 Superior alveolar artery: anterior, middle and
posterior branch (Maxillary Artery)
 Mandibular teeth:
 Inferior alveolar artery (Maxillary Artery)
Tooth Morphology
 Please look the additional notes for this section
ANY QUESTIONS