Dentine Structure Flashcards
Dentine:
Dentine:
Forms the —- of the tooth
Gives the yellow colour to the tooth
—- and so supports the hard but brittle enamel to prevent fracture during —-, dentine has some elasticity and ‘give’
Functionally, should not be considered in isolation but as a dentine-pulpal complex - it is a vital tissue
Perforated by —- from the pulp to the EDJ and carrying fluid from the pulp (dentinal fluid). Tubular structure in dentine, path odontoblasts take as they —- from the enamel-dentine junction where the odontoblast process extends into. That is the path the odontoblast take to the living position.
bulk
Resilient
chewing
tubules
retract
Give the composition of the enamel:
Inorganic: 70% weight / 50% volume - Calcium hydroxyapatite - Hexagonal prisms - Found on and between collagen fibrils (where crystals are laid down) Organic: 20% weight, 30% volume - 90% collagen type I (trace of collagen 3 and 5) - 8% non-collagenous proteins - 2% lipids Water: 10% weight, 20% volume
What are the main parts of the organic matrix?
Collagen type 1 Phosphoproteins Glycoproteins Proteoglycans Growth factors Metalloproteinases Serum-derived proteins
What are problems for bonding composites to teeth?
- Composite fillings are hydrophobic. Fluid flow outwards due to plural pressure towards EDJ limits the bonding of these agents (dentine has a water content).
- Dentine has both mineral and organic elements so a bond has to be made with both of these
- Slightly flexible so the bond has to resist movement
Give the names of the dentine types in order
Crown:
Mantle dentine
Circumpulpal dentine
Radicular:
Hyaline layer
Granular layer
Circumpulpal
What does primary and secondary dentine consist of?
Primary = mantle and circumpulpal
- laid down as tooth develops and erupts until root apex closes
Secondary = circumpulpal
- firms after apex closure
Give details on primary and secondary curvature
Primary: curved, sigmoid course from enamel-dentine junction towards the pulp
Secondary: change in direction every few um, form contour line of Owen when these coincide in adjacent tubules. Goes through quiescent and active periods which changes direction and diameter of the tubule
Give 4 bullet points on dentine tubules
- Marked branching can be seen just below EDJ
- Less obvious below this layer
- Also visible in unmineralised predentine
- Branching (and loops) responsible for granular layer of Tomes in root dentine
What is the contents of dentine tubules?
- Odontoblast process (microtubules and intermediate filaments run longitudinally, do not contain many organelles in mineralised tissue)
- Some peritubular space (but not at predentine or innermost mineralised dentine, space is filled with dentinal fluid which has a positive outwards pressure)
- Possibly smaller odontoblast processes
- Commonly beneath cusps (possibly process of antigen presenting cells, sensory terminal fibres have been identified but no obvious synapse demonstrated)
What causes sensitivity in teeth?
Hydraulic action (movement of fluid in tubule causing a change in pressure which triggers pain fibres within the pulp).
What is intratubular dentine? - what is it formed of? - what happens with age? - compare to intertubualar dentine ect
Reduces diameter of dentine tubules.
Increased with age and eventually occluded tubules.
(in root gives rise to translucent dentine).
Hypercalcified compared to intertubular dentine (15% more mineralised).
Non-collagenous matrix
- glycoproteins
- proteoglycans
- lipids
- osteonectin
- osteocalcin
- bone sialoprotein
Form almost at the same time as intertubular dentine
Is intertubular or intratubular dentine more calcified?
Intra tubular
Where does filling material penetrate into to help lock it in place?
Tubular space
What happens to the tubules next to the pulp?
Size and density of tubules increase
Explain how etching works on dentine
Strong acid, but not as strong as needed on enamel this is more mineralised.
Want to remove this mineral in dentine to expose the collagen.
Filling material can penetrate tubule but also the collagen fibrils. The fibrils are at a nanometer level and tubules at micron level. These different levels help lock and seal the material restoration onto the tooth.