Histology of Dentin

Importance of dentin

Management of dental caries, bonding of dental restorations, management of tooth sensitivity, selection of lining materials

Compare the compression strength between dentin and enamel

Similar

Compare the flexibility/hardness of dentin and enamel

Dentin is more flexible (viscoeleastic), while enamel is brittle, harder, and more mineralized

What property of dentin lends itself to its high flexibility, relative to enamel

Collagen components

What does elastic modulus tell us about dentin/enamel?

Measures a material's stiffness by quantifying its resistance to elastic deformation under applied stress (higher in enamel)

What is the significance of demineralized values for dentin/enamel physical measurements?

Underlines the importance of mineralization in the hardness of dentin

Dentin locations

Crown and tooth root, molecularly bound to tooth enamel

Describe dentin structure

Tubular, microcanals radiate from dental pulp to enamel

Dentin is considered a viscoelastic tissue due to its high degree of flexibility, why is it so vital?

Connection between dentin/pulp-dentin/pulp complex; reactivity to agonists against either party

What are odontoblast processes?

Organelle-containing structures that traverse the body of the dentin. Can branch laterally

Do odontoblast processes extend into enamel or pulp?

Yes, they can extend into enamel and/or pulp.

What can the extension of odontoblast processes into pulp lead to?

It can lend to hypersensitivity.

Describe the structure of dentin

Calcified network of collagenous fibrils and non-collagenous proteins with concentric tubules which radiate outward from the pulp to the enamel (radial arrangement of tubules); occupied by odontoblast processes

Peritubular dentin

Hypercalcified region with a small amount of organic content (proteoglycans and glycosaminoglycans); contains dentin tubules

Intertubular dentin

Exposing this region is essential for creating strong bonding during restorations

Main structural component of the dentin, collagen fibrils with smaller amounts of apatite crystals arranged roughly parallel to the fibrils

Dentin tubules trends (superficial vs. deep dentin)

Tubules increase in diameter and quantity as they get closer to the pulp (deep dentin); superficial dentin has better bonding, more intertubular dentin

What is a contributing factor to a higher ratio of intertubular dentin in superficial dentin?

Not all tubules reach all the way to the superficial layer

Dentin composition by weight

Inorganic: 70%

Organic: 20%

Water: 10%

Dentin composition by volume

Inorganic: 40-45%

Organic: 30%

Water: 20-25%

Inorganic components of dentin

Hydroxyapatite; small amounts of sodium, magnesium, chloride, carbonate, fluoride

Organic components of dentin

Type 1 collagen, aa (Hydroxyproline, glycine, alanine, proline), non-collagenous components (Lipids, phospholipids, phosphoproteins, mucopolysaccharides, enzymes-proteases)

Label this image

A: Calcified dentin

B: Uncalcified dentin (predentin)

C: Odontoblastic processes

D: Bodies of odontoblasts

Label this image

A: Dentinal tubule

B: Intertubular dentin

C: Dentinal tubule

Primary dentin

Odontoblast are critical for the formation of primary dentin until the tooth becomes functional

Secondary dentin

When contacts between antagonistic cusps are established, formation of secondary dentin starts immediately and continues throughout life

What are some causes of dentin remodeling?

Occlusal trauma, tooth wear, dental caries, cavity preparations, restorative procedures, materials causing reaction in dentin, marginal microleakage

How does the dentin-pulp complex react to stimuli?

Tertiary dentin: Appears with alterations, depending on the speed and severity of the attack, the progression of the reaction and the age of the patient.

Reactionary dentinogenesis

Smaller lesion reaches dentin, low grade inflammation, dentin passes message to pulp; pulp starts process of inflammation and odontoblasts produce tertiary dentin as protection

Reparative dentinogenesis

More pronounced lesion and stimulus, has damaged odontoblasts, stem cell recruitment and differentiation into odontoblast-like cells which produce tertiary dentin

Reparative dentin

Does not result from the activity of odontoblasts or associated cells but specifically from pulp progenitors implicated in the formation of bone-like unorganized dentin.

Sclerotic dentin

Dentin that has become translucent due to calcification of the dentinal tubules. As a result of injury or normal aging. Also called transparent dentin.

Hybrid layer of dentin

Intermediate layer consisting of hydrophilic resin monomers infiltrated in demineralized dentin surfaces

Hydrodynamic component of dentin hypersensitivity

Heat/cold/air/mechanical pressure affects fluid movement; mechanical disturbance of odontoblast processes, potentially reaching pulp tissue