The Anatomy, Physiology and Morphology of Teeth

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

2. 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

3. 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

4. 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

5. Enamel Periodontal Ligaments Dentine Dentinal Tubules Cementum Pulp Alveolar Process Cortical Plate Spongy Bone

6. 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

9. 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)

10. The complexity of the root canal

11. 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

12. 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

13. 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

14. 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)

15. The Branches of the Trigeminal Nerve

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

17. Tooth Morphology • Please look the additional notes for this section

18. ANY QUESTIONS