(4) Dentino-pulpal Complex Flashcards
What forms the bulk of the tooth?
Dentine
Is dentine a live tissue?
yes!
Forms throughout life
What cells form dentine?
odontoblasts
Where are the parallel tubules located in dentine?
Mineralised collagen matrix
What is dentine harder than?
Harder than bone and cementum
What makes dentine so strong?
Its tubular nature renders it strong (high compressive, tensile and flexural strength).
What are the percentages of inorganic, inorganic and water in dentine?
Dentine is composed of 70% inorganic component, 20% organic component and 10% water by weight.
Why is dentine more soluble than enamel?
The hydroxyapatite is more carbonate rich
Smaller than enamel
Where are the crystals found in dentine?
crystals are found on and between collagen fibrils.
What are the organic components of dentine?
Collagen (mainly type I) forms 90% of the organic component.
Dentine phospho-proteins, proteoglycans and other proteins are also present.
What is the chemical composition of dentine?
Hydroxyapatite crystals
What forms over 90% of the organic matrix
Collagen type l
What is the main phosphoprotein of denting
Phosphophoryn/ dentin phospho-protein
most acidic protein known and can bind calcium ions
Allows it to be important in mineralisation
What is a feature of phosphophoryn?
Due to its high calcium ion binding properties, it has been implicated in mineralisation.
What are the main proteoglycans of dentin?
biglycans and decorin
What is the role of proteoglycans is dentin?
Proteoglycans have an important role in collagen assembly, cell adhesion, migration, differentiation and proliferation.
What are the main glycosaminoglycans of dentin?
chondroitin-4- sulphate and chondroitin-6-sulphate.
What are other acidic components of the organic matrix of dentin?
osteonectin, osteopontin
What are some growth factors found in dentin?
insulin-like growth factor and transforming growth factor. They are absorbed from circulating tissue fluid.
What are phospholipid thought to be involved in?
involved in the formation and growth of apatite crystals. - organic matrix
Where do denting tubules extend from and to?
Dentinal tubules extend from the pulp surface to the amelo- dentinal and the cemento-dentinal junctions.
What course do the dentin tubules follow?
Curved sigmoid course
Primary curvature
Name structures A and B
What type of section is shown here?
Cross section
Partial demineralised section
Name structures A-C
What side of the dentin is thicker and which is thinner?
The tubules are 2.5μm in diameter at the pulpal end and 1μm or less at the Enamel end.
Why do the dentin tubules become closer together at the pulpal end?
As the odontoblasts retreat inwards, they occupy a smaller area, thus the tubules become closer to each others.
What cross-sectional area occupies more dentin tubules, enamel-dentin junction or the pulps end?
PULPAL END
22% of the cross sectional area near the pulp is occupied by dentinal tubules.
* 2.5% at the enamel-dentine junction.
What does this image show?
Contour lines of Owen
Secondary curvatures, if they coincide in adjacent tubules they give rise to contour lines of Owen (arrowed).
Where do dentin tubules branch?
near enamel-dentine junction
What happens to terminal branches at the root?
They loop
What forms the wall of the newly formed dentin tubule at the pulp?
Mineralised type 1 collagen
What is called intratubular dentin?
Tubules are lined with peritubular (intratubular) dentin consisting of a layer of highly mineralized matrix material made primarily of apatite crystals. The intertubular dentin, which lies between the tubules, is a less-calcified matrix that consists of some apatite crystals embedded within a collagen matrix.
Maturation Reduces size of lumen
What is the role of the organic dentin phospho-proteins?
Only present in small amounts
Integral in the mineralisation of dentin
