Dentine Flashcards
What is the composition of dentine?
65-70% inorganic hydroxyapatite, 20% organic matrix and 10% water.
Collagen fibres make up mostly all of the organic matrix with principal collagen fibre is type 1
What is mantle dentine?
The first formed in the crown and most peripheral layer beneath the enamel.
What is circumpulpal dentine?
Forms the bulk of the dentine between the mantle layer and zone of mineralisation, typically in outer part of the crown
How does interglobular dentine result?
When calcospherites do not fuse completely with the advancing mineralisation front
What is predentine?
Innermost un-mineralised layer, where new dentine is being deposited throughout life.
What appearance does predentine have when dyed with haematoxylin and eosin?
Pale appearance
What is secondary dentine?
Seen in older teeth at the inner, pulpal part of the circumpulpal dentine, continuous with primary dentine
What is tertiary dentine?
Hard tissue deposited on the pulpal surface in response to an external stimulus (caries, attrition) - provides a barrier to the progress of caries and toxins
What is reparative dentine?
Dentine forming after a stimulus has killed the original odontoblasts, these cells differentiate from odontoblast like stem cells, much more irregular than circumpulpal dentine
What results in 20um spaced Andresen lines?
Changes in collagen fibril orientation
What are short period markings seen as alternating light and dark bands called?
Von Ebner lines
What are lines associated with the primary curvatures of the dentinal tubules called?
Schreger lines
What are lines associated with the secondary curvatures of dentinal tubules called?
Contour lines of Owen
What physical property differs dentine from enamel?
Dentine is flexible
Where do dentinal tubules run?
From the pulpal surface to the enamel-dentine and cementum-dentine junctions.
What dentine is deposited on the walls of dentinal tubules to make their lumens smaller?
Peritubular dentine
What shape are primary curvatures of dentinal tubules?
Curved and sigmoid
Do secondary curvatures have smaller changes in direction of the tubules?
Yes
What may be responsible for the appearance of the granular layer of Tomes?
Looping of the terminal part of the tubules
Do dentinal tubules get longer or shorter going from the pulp to the EDJ?
Shorter
Does dentine formation begin before enamel?
Yes
Which surface is the most recently formed dentine on?
Pulpal and is called pre-dentine
Does dentine formation continue after tooth eruption?
Yes and throughout the life of the pulp
What is the second most abundant constituent of dentine?
Dentine phosphoprotein
How does the amount of translucent dentine change with age?
Increases
How does peritubular dentine differ from intertubular dentine?
Lacks a collagenous fibrous matrix and is more mineralised than intertubular dentine
How do dead tracts form?
Primary odontoblasts are killed by an external stimulus, the empty tubules remain air filled and transmitted light under the microscope will be internally reflected and the tubules appear as dark tracts.
What are the three proposed mechanisms of dentine sensitivity?
1) Direct innervation
2) Odontoblasts acting as sensory endings
3) Hydrodynamics (fluid flow)
What is the hydrodynamic fluid flow theory?
An effective stimulus triggers a flow of fluid within the tubules, the movement being sufficient to depolarise nerve endings either within the inner parts of tubules or between odontoblasts at the pulp-predentine junction and to the subodontoblastic neural plexus.
Where is interglobular dentine found adjacent to?
Mantle layer in the crown
