Dental Anatomy Quiz

Enamel

• Prismless enamel is about 30 μm thick and may be more heavily mineralized.
• It is a structureless outer layer of enamel, but not composed of enamel rods.

Enamel Structure

• Enamel is composed of rod sheaths, cementing inter-rod substance, and millions of enamel prisms.
• It does not contain tubules.

Enamel Solubility

• Enamel is soluble when exposed to acidic conditions.
• Fluoride ions decrease the solubility of surface enamel when present during enamel formation.
• Fluoride affects the chemical and physical properties of the apatite mineral.

Enamel Features

• Enamel is permeable to certain ions and molecules.
• The density of enamel increases from the surface to the DEJ.
• The solubility of enamel decreases from the surface to the DEJ.

Cementum-Enamel Junction (CEJ)

• In about 10% of teeth, enamel and cementum do not meet.
• The CEJ is a wavy line.
• The rounded projections of enamel fit into the shallow depressions of dentin, contributing to a firm attachment.

Secondary Dentin

• In multirooted teeth, secondary dentin tends to be thicker on the roof and floor.
• It becomes less sensitive, and tubular fluid flow becomes more restricted.
• The lumen of tubules becomes smaller.

Dentin Permeability

• There is a continual dentin fluid flow from the pulp toward the external surface of the tooth.
• Coronal dentin is more permeable than root dentin.
• Deep dentin is a less effective pulpal barrier compared with superficial dentin.

Cementodentinal Junction

• The attachment of cementum to dentin is very durable.
• The junction is wavy in outline.
• In about 10% of teeth, the openings of the dentinal tubules are not covered by enamel or cementum.
• Abrasion, erosion, and caries may denude dentin of its cementum covering, leading to sensitivity.

Reparative Tertiary Dentin

• It is generated by the odontoblast-like cells.
• It appears as a localized dentin deposit on the wall of the pulp cavity immediately subjacent to the area on the tooth that received the injury.
• It is not generated by the secondary odontoblasts.
• It does not have the same structure as primary and secondary dentin.

Dentin

• Dentin is normally yellow-white and slightly darker than enamel.
• It is flexible, and its flexibility helps support the more brittle, less resilient enamel.
• Human dentin is composed of approximately 90% to 92% (by volume) inorganic material.
• It is not brittle.

Dentinal Tubules

• Dentinal tubules are small canals that extend across the entire width of dentin.
• Each tubule contains the cytoplasmic cell process (Tomes fiber) of an odontoblast.
• Each dentinal tubule is lined with a layer of peritubular dentin.
• The lumen of the tubules does not have a constant diameter.

Physiologic Dentin Sclerosis

• It is also known as dentin sclerosis resulting from aging.
• The walls of the dentinal tubules gradually thicken, through ongoing mineral deposition, with age.
• The dentin becomes harder and denser.
• It is not thicker on the roof and floor than on the side in multirooted teeth.

Test your knowledge of dental anatomy with these questions about enamel structure and composition.