Dentinogenesis: Odontoblast Differentiation

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.

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.