OCB02-1016 Dentine Flashcards
What is responsible for the yellow colour of the tooth?
Dentine
What is dentin perforated by?
Tubules
What are tubules?
They go from the pulp to EDJ and carry fluid from the pulp
What % of dentine is inorganic?
70%
What % of dentine is organic ?
20%
What % of the organic dentine is type I collagen?
90%
What % of the organic dentine is non collagenous proteins?
8%
What % of the organic dentine are lipids?
2%
What % of dentine is water?
10%
How does the hydrophobic composite filing pose a problem?
fluid flow creates a wet environment around the oral cavity
The outward fluid flow limits the penetration of bonding agents
What are the two types of dentine?
coronal and radicular dentine
What are the two types of coronal dentine?
Mantle dentine and circumpulpal dentine
What is mantle dentine?
The outermost layer of dentine that lies just below the enamel
What is circumpulpal dentine?
Circumpulpal dentine lies below the mantle dentine and extends round the crown and down into the root
What is the difference between mantle and circumpulpal dentine?
Mantle dentine is slightly less mineralised and more porous than circumpulpal dentine
What are the two types of radicular dentine?
Hyaline layer of Hopewell Smith
Granular layer of Tomes
What is the hyaline layer of Hopewell Smith?
Next to the cementum and has no dentinal tubules
May serve to bond the cementum to the dentine and is the last dentine layer to mineralise
What is the granular layer of Tomes?
Beneath the hyaline layer
Its less mineralised than the circumpulpal layer
Collagen fibres run parallel to the root surface
What pattern does the primary curvature of the tubules follow from the EDJ?
A sigmoidal S-shaped pattern due to overcrowding of odontoblasts
When is the secondary curvature of the dentinal tubules formed?
The tubules change direction every few micrometer
What layer of dentine are the branching and loops of the dentinal tubules responsible for?
Granular layer of Tomes in root dentine
What is the odontoblast process responsible for?
Secretion of hydroxyapatite crystals and mineralisation of the matrix
Where is peritubular space not present with dentinal tubules?
Predentine level or innermost mineralised dentine
What is another word for peritubular dentin?
Intratubular dentine
What is the peritubular space filled with?
Dentinal fluid which exerts a positive outwards pressure
What does peritubular dentin do?
It creates the wall of the dentinal tubules
How does the growth of pertiubular dentine affect the diameter of the dentinal tubules?
As the peritubular dentine grows, it reduces the size of the dental tubules
How does the amount of peritubular dentine change with age?
It increases and eventually occludes the tube
What is the difference between peritubular and interlobular dentine?
Peritubular dentine is hyper calcified compared to interlobular
Where about are the diameter and density of the tubules the greatest?
Near the pulp
What is the purpose of etching?
To remove the smear layer of microcrystalline and organic particle debris on root canal walls to prevent bacteria entering the dentinal tubules
What are von-ebner lines?
Visible as light-dark band patterns that run perpendicular to dentinal tubules
Where are von-ebner lines present?
Circumpulpal dentine
What conditions can Andersen lines be seen?
Under polarised light
What slows the development of Andersen lines?
Birth or death
Where is the neonatal line seen?
All primary teeth and permanent molars
How does the neonatal line differ from other Retzius lines?
It is darker and larger
What does the initial matrix become?
Mantle dentin
What are the collagen fibres in the mantle dentin that are perpendicular to IEE called?
Von Korff Fibres
What is unmineralised dentine called?
Predentine
What staining appearance does predentine have?
Pale
What is the area between predentine and mineralised dentine called?
Metadentine
What are circular areas of mineralisation called?
Calcospherites
What is interglobuar dentine?
Areas that haven’t been fully calcified and only primary mineralisation has occurred in the predentine
Formed by the failure of calcospherites to fuse
Where is interlobular dentine located?
Below the mantle dentin the the granular layer
When is secondary dentin formed?
Formed after root formation is complete, after the tooth has erupted
What is the structure of secondary dentin?
Simiar to primary dentin- contain tubules
Tubular patterns are less regular
Odontoblasts become more crowded
How does growth of secondary dentin differ to that of primary?
Secondary dentin grows much slower in increments
What clinical impact does secondary dentin have?
It reduced the size of the pulp chamber and root canal diameter with age which can make endodontics more difficult
When does tertiary dentine form?
In response to external stimulations such as cavities
What are the two mechanisms by which tertiary dentine is formed?
Reactionary formation
Reparative formation
What is reactionary formation of tertiary dentine?
Dentin is formed from pre-existing odontoblast
What is reparative formation of tertiary dentine?
New odontoblasts are formed from pulpal progenitor cells due to death of previous odontoblasts
How is translucent dentin formed?
Due to dentinal tubules being filled in response to external stimuli such as attrition or slow advancing caries
In what way is the mineral composition of translucent dentine and peritubular dentine different?
Translucent is composed of crystalline and may contain salivary components due to caries
What are dead tracts?
Empty tubules that are sealed at the pulpal end by tertiary dentin
How are empty tubules formed?
Due to the death of odontoblasts or odontoblasts that have stopped their function
Where are dead tracts more common
Secondary dentin
