LECTURE 2 - Anatomy

General Tooth Anatomy and Introduction to Incisors

External Tooth Anatomy

  • Apex: The very end of the root of the tooth.

  • Cervical Line: The junction where the crown of the tooth meets the root, and also marks the end of the tooth where it transitions to the gum line. Its appearance varies by tooth.

  • Crown: The visible part of the tooth when looking in a mirror.

  • Incisal Edge: Found on anterior teeth, this is the end of the crown closest to the occlusion point.

  • Occlusal Surfaces: Found on posterior teeth, these are the chewing surfaces.

Number of Roots by Tooth Type

The number of roots varies depending on the specific tooth:

  • Incisors and Canines: Typically have one root. While variations can occur, for foundational knowledge, assume one crown and one root.

  • Premolars:

    • Upper First Premolars: Have two roots.

    • Other Premolars (Upper Second, Lower First, Lower Second): Have one root.

  • Molars:

    • Upper Molars (First and Second): Have three roots. These are typically one mesial, one distal, and one palatal root, making them very large teeth.

    • Lower Molars (First and Second): Have two roots. They are also large teeth but differ from upper molars in root count.

    • Third Molars: Exhibit significant variation in root structure and are not a primary focus in this course.

Internal Tooth Anatomy

All teeth share a similar internal structure, though this example is observed in a molar:

  • Enamel:

    • The outermost layer of the crown.

    • Composed of 95%95\% mineral.

    • The hardest mineralized tissue in both the tooth and the entire body. Its high mineralization is why teeth can be used for identification (e.g., after fires or explosions) as they resist burning and disintegration.

    • It forms the exterior surface of the crown.

  • Dentin:

    • The layer located directly beneath the enamel.

    • Composed of 70%70\% mineral (less than enamel).

    • It surrounds the pulp, providing protection from aggressions originating from the mouth.

    • It also supports the structural integrity of the enamel, acting as a middle layer.

  • Cementum:

    • Composed of 50%50\% mineral.

    • A thin, mineralized tissue layer covering the tooth root surfaces.

    • It is part of the periodontal structure and plays a crucial role in anchoring the tooth in the alveolar bone, working with the periodontal ligament.

  • Pulp Chamber (Pulp):

    • A non-mineralized tissue located internally.

    • Houses all the essential innervation (nerves) and vascularization (blood vessels, including blood) that supply the tooth.

    • This is the area targeted during an endodontic (root canal) treatment. If infected, the nerves and vascularization are removed from the pulp chamber and root canal, replaced with a different material, to alleviate pain and prevent swelling.

  • Root Canal: The extension of the pulp chamber down into the roots of the tooth.

  • Gingiva: The professional term for gums.

  • Periodontal Ligament: A structure that helps firmly anchor the tooth in its socket within the bone.

  • Alveolar Bone: The bone tissue in which the tooth is embedded.

  • Blood Vessels and Nerves: These begin in the root and extend upwards into the pulp chamber, providing vitality to the tooth.

  • Neck: A transitional area, sometimes described as the end of the crown, moving towards the root.

Mineral vs. Non-Mineralized Tissues

  • Mineral Tissues: Cementum, Dentin, Enamel.

  • Non-Mineralized Tissue: Pulp (contains nerves, blood vessels, and blood).

Specific Anatomical Features and Terminology

  • Bifurcation Space:

    • The space found between two roots.

    • Only present in multi-rooted teeth (e.g., first premolars and all molars).

    • Crucial area for cleaning and addressing periodontal issues due to potential contamination accumulation.

  • Cementoenamel Junction (CEJ): The distinct anatomical line where the enamel of the crown meets the cementum of the root.

  • Pulp Horn:

    • A part of the pulp chamber that extends closer to the dentin, resembling horns.

    • It is the most likely part of the pulp chamber to be encountered first during deep cavity preparation for caries removal.

  • Cusps:

    • Elevations found on the incisal or occlusal part of the crown.

    • Canines possess one cusp.

    • Posterior teeth (premolars and molars) have multiple cusps, the number varying by tooth.

    • Important: Incisors do NOT have cusps; they feature incisal edges instead. (The letter F on the diagram refers to enamel and CU refers to cusps).

  • Cingulum:

    • A rounded elevation resembling a small ball, located on the lingual (tongue side) surface of anterior teeth.

    • Situated in the cervical third of the crown.

    • Its prominence varies among individuals and can sometimes be felt with the tongue.

  • Fossa:

    • An irregular depression or concavity on the tooth surface.

    • Examples include the lingual fossa of incisors and the central or triangular fossae in molars.

    • It is the opposite of a ridge.

  • Ridge:

    • An elevation on the enamel surface.

    • Marginal Ridge: Found at the edges of a tooth (e.g., mesial and distal marginal ridges on the lingual surface of incisors).

    • Other types, such as triangular, transverse, and oblique ridges, are typically found in posterior teeth.

    • The ridge is an elevation, contrasting with the depression of a fossa.

  • Sulcus:

    • A broad depression or