Dentin Flashcards
Which substance gives teeth their yellow colour?
Dentin
What is the composition of dentin by weight and volume?
Inorganic - 70% w, 50% v
Organic - 20% w, 30% v
Water - 10% w, 20% v
Describe the inorganic component of dentin.
Primarily hexagonal hydroxyapatite prisms found on or between collagen fibrils
What are the dimensions of the hydroxyapatite prisms in dentin?
10x35x100nm
Describe the organic component of dentin.
90% type I collagen (large diameter - 100nm) and traces of type III and V
8% non-collagenous proteins
2% lipids
Which direction does pulpal pressure push dentinal fluid?
Outwards
Why is the water component in dentin important practically?
Problem for binding composites which are hydrophobic
Limits penetration by bonding agents
What is the primary curvature in dentin?
Curved sigmoid course of dentinal tubules/odontoblasts from enamel to pulp
What is the secondary curvature in dentin?
Odontoblasts changing direction every few microns (diurnal)
What are the contour lines of Owen?
In dentin, when the diurnal changes in direction of odontoblasts line up
How can you spot mantle dentin?
Marked branching seen just below EDJ in coronal dentin
What is the mantle dentin equivalent in the root?
Granular layer of Tomes
What is contained in a dentin tubule? (4)
Odontoblast process and smaller ones
Dentinal fluid
Processes of antigen-presenting cells
Sensory nerve terminal fibres
Where is peritubular space not found?
Predentin
Most recently mineralised dentin
Where are the processes of antigen-presenting cells and sensory nerve terminal fibres usually found?
Beneath cusps in dentinal tubules
How do the sensory nerve terminal fibres in dentin detect stimuli?
Hydraulic movement of dentinal fluid within the tubule
What is another name of intratubular dentin?
Peritubular dentin
Is intratubular dentin mostly primary or secondary dentin?
Secondary (fills up tubules)
In the root, what does intratubular dentin give rise to?
Translucent dentin
How does the mineral content of intratubular dentin compare to intertubular dentin?
Hypercalcified - 15% more mineralised
What substances make up the organic non-collagenous matrix intratubular dentin? (6)
Glycoproteins
Proteoglycans
Lipids
Osteonectin
Osteocalcin
Bone sialoprotein
How does the acid etch used on dentin compare to that used on enamel and why?
Weaker
Less mineralised than enamel
What is the smear layer?
Debris layer, 15-20um thick, produced when friction occurs
Why do we use acid etch before bonding?
Acid removes mineral to expose collagen fibrils (nm) and removes smear layer
Resin can penetrate at um and nm levels to create a strong bond
