Tooth Anatomy and Histology




tooth
Fig 1 Cross section of a tooth (Teeth-Adult, 2009)

A tooth is made up of the following structures:-
  1. Enamel
  2. Dentin
  3. Pulp Cavity
  4. Cementum
Enamel

  • White (translucent), hard and resistant layer covering the crown of the tooth, protecting the tooth from mechanical and chemical attack.
  • Made up of enamel rods that run parallel to each other, projecting perpendicularly from the dentin surface.
  • Each enamel rod attaches directly to the dentin underneath, preventing penetration of cracks in the enamel into the dentin.
  • Enamel meets the dentine at the enamel-dentin junction (EDJ) and meets the cementum at the cemento-enamel junction (CEJ).
Dentin
  • Hard, yellowish material that lies underneath the enamel, surrounding the pulp chamber of the tooth
  • Sensitive to stimuli (even though it is not innervated) due to movement in fluid in the odontoblast projections in dentin tubules originating from the inner surface of the dental pulp perpendicularly outwards to the tooth surface until just before the enamel.
  • Surrounds the entire nerve/pulp of the tooth.
  • Forms the pulpo-dentin organ of the tooth with the pulp.

Pulp Cavity
  • Dental pulp is a pink and soft organ consisting connective tissue, blood vessels and nerve axons.
  • Involved in dentinogenesis (the process of building dentin) that is important for:
    • Tooth hydration
    • Dentin elasticity (to absorb shock and prevent fracture)
  • Crowns of teeth contain the coronal pulp while radicular pulp extends from the cervical part of the crown to the apex (tip) of the root.
  • Radicular pulp opens into periapical connective tissue at or 1-3mm from the tip of the root. This opening is called the apical foramen. Most infections spread through here from the pulp to the periapical tissue as blood enters and exits the dental pulp from this point, accompanying the nerves.
  • Relatively larger in children, replaced with hard structures (dentin and enamel) from the outside to the inside of the tooth, faster on the floor of the coronal pulp.
Cementum

  • Relatively soft bony tissue that covers the root surface.
  • Meets the enamel in a line surrounding the tooth called the cement-enamel junction (abbreviated as CEJ).
  • Attached to the periodontal ligament to be attached to the bony socket of the alveolar bone supporting the tooth.
  • When exposed due to recession of the gum as in old age, it is easily worn off.
  • Attachment surface for the periodontal ligament to the alveolar bone.
Tooth Anatomy and Histology - Cariology
Fig 2. Tooth anatomy (Martin S. Spiller, 2009)

The supporting structures of a tooth:-

  1. Periodontal ligament
  2. Alveolar bone
  3. Gingiva
Periodontal ligament
  • A soft tissue sheath that cushions the tooth in its socket in the alveolar bone.
  • Prevents ankylosis (the direct contact between tooth and bone).
  • Made up of fibrous connective tissue running perpendicular to the tooth and alveolar bone surfaces and almost parallel to each other.

Alveolar bone
  • Supports the tooth - is resorbed once the tooth is extracted.
  • Consists of two parts: lamina dura and cancellous bone.
  • Cancellous bone contains trabeculli that compartmentalize bone marrow.
Gingiva
  • Separates the dirty oral environment from the rest of the body, preventing infection of the alveolar bone (osteomyelitis)




REFERENCES:

Teeth-Adult (2009). Virtualmedicalcentre.com. Retrieved Oct 29, 2009 from http://www.virtualmedicalcentre.com/anatomy.asp?sid=23

Martin S. Spiller (2009). Tooth Anatomy. Retrieved Oct 08, 2009 from http://www.doctorspiller.com/tooth_anatomy.htm





Links

An Introduction | Tooth Anatomy and Histology | Dental Caries | Dental Caries - An Infectious Disease or a Chronic Disease |

Early Caries and Enamel Changes | Caries Progression and Dentine Changes | Pulpo-dentinal Changes

Root Surface Caries and Changes in the Cementum
| Dental Fluorosis | Erosion of the Teeth | Conclusion


More pages