Dentinogenesis: Odontoblast Differentiation

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Questions and Answers

Where does odontoblast differentiation occur?

Along the boundary between the epithelial cells of the enamel organ and the ectomesenchymal cells of the dental papilla (correct)

In the dental papilla, away from the boundary with the enamel organ

In the enamel organ

In the ectomesenchyme, separate from the influence of the enamel organ

What is the role of signalling molecules and growth factors in odontoblast differentiation?

They have no influence on odontoblast differentiation

They inhibit the differentiation of ectomesenchymal cells

They attract undifferentiated cells of the dental papilla to the boundary (correct)

They repel ectomesenchymal cells from the boundary

What happens to ectomesenchymal cells adjacent to the epithelial boundary?

They differentiate into epithelial cells

They remain unchanged

They rapidly decrease in size and number

They elongate and develop organelles for protein synthesis (correct)

What is the final result of odontoblast differentiation?

The secretion of the dentine matrix Signup and view all the answers

What is the orientation of epithelial cells relative to the boundary with the enamel organ?

Oriented relative to the boundary Signup and view all the answers

What happens to ectomesenchymal cells closest to the boundary with the cells of the enamel organ?

They elongate, polarize, and differentiate into odontoblasts Signup and view all the answers

What type of collagen is present in the mantle predentine matrix?

Type III Signup and view all the answers

What is the orientation of type I collagen fibrils in the circumpulpal predentine?

Parallel to the secretory surface Signup and view all the answers

What is left behind in the matrix by the odontoblasts?

An odontoblast process Signup and view all the answers

What separates the odontoblast layer from the mineralized dentine?

Unmineralized, collagen-rich predentine matrix Signup and view all the answers

What promotes hydroxyapatite crystal growth in dentine mineralization?

_matrix vesicles containing phosphate-sequestering enzymes and proteins Signup and view all the answers

During dentinogenesis, when does dentine matrix production begin?

Before enamel matrix production Signup and view all the answers

What is the function of matrix vesicles secreted by odontoblasts?

To promote hydroxyapatite crystal growth Signup and view all the answers

What type of mineralization occurs in circumpulpal dentine?

Linear and globular mineralization Signup and view all the answers

What is the significance of incremental growth lines in dentine?

They signify changes in odontoblast activity over time Signup and view all the answers

What is unique about dentine deposition compared to enamel?

Dentine deposition occurs for many years following tooth eruption Signup and view all the answers

What type of mineralization occurs in mantle dentine?

Globular (calcospheric) mineralization Signup and view all the answers

What is the role of odontoblasts in dentinogenesis?

To secrete matrix vesicles that promote mineralization Signup and view all the answers

What type of lines represent supra-daily, non-rhythmic variations in dentine production?

Contour lines of Owen Signup and view all the answers

What can cause changes in dentine deposition rates?

All of the above Signup and view all the answers

What is the name of the lines that are formed by the coincidence of secondary curvatures of dentine tubules during dentinogenesis?

Lines of von Ebner Signup and view all the answers

What is the purpose of this lecture?

To distinguish between different incremental and non-incremental lines found in dentine Signup and view all the answers

What type of lines are preserved in ground sections but not in paraffin sections?

Lines of von Ebner Signup and view all the answers

What is the result of hypomineralisation during dentinogenesis?

Changes in dentine deposition rates Signup and view all the answers

What do the incremental growth lines in dentine signify?

Daily variations in dentine production Signup and view all the answers

What is the average width of incremental line growth in human dentine?

4-5 µm Signup and view all the answers

What do the Andresen lines represent in dentine?

Multi-day incremental lines spaced 6-10 days apart Signup and view all the answers

What do tetracycline labeling experiments show about Andresen lines?

They are long-period (multi-day) lines Signup and view all the answers

What is the significance of the collagenous matrix in dentine growth?

It represents structural variations in dentine growth Signup and view all the answers

According to Emken et al. (2021), what is the significance of incremental growth lines in dentine?

They represent daily variations in dentine production Signup and view all the answers

Study Notes

Dentine Matrix Production

Dentine matrix production initiates before enamel matrix formation.
Odontoblasts secrete a mantle predentine matrix consisting mainly of type III collagen, known as von Korff’s fibers.
As odontoblasts grow during dentinogenesis, they produce type I collagen fibrils of circumpulpal predentine, oriented parallel to the secretory surface.
Odontoblasts leave behind cellular extensions called odontoblast processes, resulting in the formation of dentine tubules.
An unmineralized, collagen-rich predentine matrix always separates the odontoblast layer from mineralized dentine.

Dentine Mineralization

Odontoblasts secrete matrix vesicles that contain enzymes and proteins to facilitate hydroxyapatite crystal growth, acting as "seed" for mineralization.
Initial mineralization occurs in mantle dentine through these matrix vesicles.
Circumpulpal dentine mineralization involves both calcospheric (fast) and linear (slow) processes, with odontoblasts contributing to both mechanisms.

Odontoblast Differentiation

Occurs within the dental papilla at the interface between epithelial cells of the enamel organ and ectomesenchymal cells.
Undifferentiated ectomesenchymal cells are attracted to this boundary by signaling molecules from the enamel organ.
Rapid enlargement and division of these cells lead to the elongation of those nearest to the epithelial boundary, which then differentiate into odontoblasts.

Dentine Deposition Rates

Dentine continues to be deposited for years after tooth eruption, unlike enamel.
Incremental growth lines, such as lines of von Ebner, indicate daily variations in dentine formation due to fluctuations in odontoblast activity.
Tetracycline labeling has shown that incremental growth lines preserve daily records of growth, with widths around 4-5 µm.

Non-Incremental Growth Lines

Contour lines of Owen represent supra-daily variations in dentine production caused by factors such as illness or nutrition changes.
The neonatal line marks a significant physiological change occurring at birth.
Multiple factors may contribute to the formation of non-incremental lines, such as the curvature of dentine tubules and hypomineralization.

Summary of Key Concepts

Dentine and pulp originate from the tooth bud.
Major steps in odontoblast maturation, dentine matrix secretion, and mineralization are essential for understanding tooth development.
Distinction between incremental (daily/weekly) and non-incremental lines found in dentine is crucial for interpreting dental growth patterns.

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Description

Learn about the process of odontoblast differentiation in dentinogenesis, including the role of signalling molecules and growth factors. This quiz is based on Ten Cate's Oral Histology, 8th Edition, Fig. 8-11.