The Anatomy Physiology and Morphology of Teeth By

The Anatomy, Physiology and Morphology of Teeth By Dr. Juliana Mathews

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

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

Tooth Anatomy continued Ø Periodontium: Ø Alveolar process: bony extensions of the maxilla and mandible that support teeth Ø Cortical Plate: dense outer layer of bone covering the spongy (cancellous) bone Ø Periodontal ligament : Ø Periodontal fibres attach the roots to the alveolar bone Ø has a nerve and blood supply Ø provides an elastic cushion between the tooth and bone Ø 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 Ø Pulp chamber is found on the coronal part of the tooth Ø Reduces in size with age due to secondary dentine due to physiological or pathological reasons Ø Orifices to the root canal are found on the floor of the pulp chamber Ø Canals taper towards the apex Ø 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. 5 mm-1 mm from the anatomical apex Ø New layers of cementum are constantly being laid down, therefore the centre of the foramina deviates from the apical centre Ø Lateral canals can develop between the main body of the root canal and the periodontal ligament space Ø Accessory canals can develop in the apical region forming the apical delta Ø 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 Ø Lateral canals can be impossible to instrument and can compromise obturation

Root canal system continued Ø Some roots can have more than one canal and they don’t always merge Ø 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 Ø 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 Ø Eg. Some maxillary second premolars can have two roots (usually are single rooted) or a single root with 2 canals Ø 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: Ø consist of sensory (afferent) fibres, sympathetic fibres and parasympathetic fibres Ø sensory fibres pass through the apical foramen and end at the peripheral pulp Ø sensory nerve fibres originate from the trigeminal ganglion Ø C –fibres: Ø Unmyelinated, high threshold fibres responding to mechanical, thermal or chemical stimulation Ø Dull, poor localized pain Ø A- delta fibres: Ø myelinated, low threshold mechano- receptors Ø sharp localized pain Ø 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 Ø Trigeminal Nerve: (CN V) Ø Three sensory branches Ø Opthalmic branch supplies the orbit and forehead Ø Maxillary branch supplies the maxillary sinus and upper jaw teeth Ø Mandibular branch supplies the tongue and the lower jaw teeth Ø Facial Nerve: (CN VII) Ø Motor and sensory branches Ø Innervates Ø muscles of facial expression Ø taste buds of the anterior 2/3 of the tongue Ø salivary glands

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

The Branches of the Trigeminal Nerve

Blood supply Ø Maxillary teeth: Ø Superior alveolar artery: anterior, middle and posterior branch (Maxillary Artery) Ø Mandibular teeth: Ø Inferior alveolar artery (Maxillary Artery)

Tooth Morphology Ø Please look the additional notes for this section

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