Dentin
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What are 5 distinguishing properties of dentin?
• Dentin is sensitive • Dentin is permeable • Dentin is formed throughout life • Dentin is softer than enamel • Dentin has greater compressive and flexural strength than enamel
What colour is dentin?
Pale yellow
Rank in order of hardness: Dentin, Cementum, Enamel
• Enamel • Dentin • Cementum
What forms dentin?
Odontoblasts
Where are the odontoblasts which form dentin found?
Outer border of the dental pulp
Describe the gross composition of dentin by volume
50% inorganic 30% organic 20% water
What is the main component of the organic component of dentin?
Collagen (principal fibril is Type I)
How do the collagen fibres run with respect to the pulp?
In parallel to the pulp surface
Name 2 other molecules which can be found in the organic component of dentin
• Dentine phosphoproteins 2. Proteoglycans
What 3 things can be found in dentinal tubules?
• Odontoblast processes • Afferent nerve axons • Dentinal fluid
What is a major feature, with regards to shape, of dentinal tubules
The have curvatures
What is a contour line of Owen?
Secondary curvatures which coincide in adjacent dentinal tubules
Where is a contour line of Owen usually found?
Junction of primary and secondary dentin
What is the function of dentinal tubules branching?
Allows intercellular communication
Where does the most profuse branching of dentinal tubules occur?
Dentinoenamel junction
What are 2 ways dentin can be defined due to its relationship with dentinal tubules?
• Peritubular dentin 2. Intertubular dentin
What is peritubular dentin?
Creates the wall of the dentinal tubule
What is the intertubular dentin?
Found between dentinal tubules
What are the 2 main differences between peritubular dentin and intertubular dentin?
• Peritubular dentin lacks a collagen matrix 2. Peritubular dentin is more mineralised
What are 2 ways to classify dentin with regards to the time of its development?
• Predentin • Mineralised a) Primary b) Secondary c) Tertiary
What is Predentin?
Innermost, unmineralised layer where new dentin is being deposited by odontoblasts
What are the 2 components of primary dentin?
• Mantle dentin 2. Circumpulpal dentin
What is mantle dentin?
Outermost layer of the crown, with many tubule branches, which prevents any cracks in enamel spreading to dentin
What is circumpulpal dentin?
Lines the pulp chamber and makes up the majority of dentin within the crown