OB D9: Pulpo-dentinal complex : Dentine Flashcards
what is the composition of dentine?
mineral - 70%
Matrix- 20%
water - 10%
Name some features of dentine.
- Specialised connective tissue -Hard (KHN 75)
- Strong and resilient
- ~70% mineral - hydroxyapatite
- ~20% organic - collagen
what is the direction of collagen fibres in dentine?
- mainly parallel to ADJ
- Gives dentine strength
In what dentine are the collagen fibres not parallel to the ADJ?
mantle
what structures make up dentine?
dentinal tubules
what are the tubules continuous with?
pulp
how many tubules are there?
15 000-65 000 tubules per mm2
what do tubules contain?
- cell processes
- nerves
- fluid - flows out
Is dentine vital?
yes
what is the difference in number of tubules per mm2 in amelodentinal junction and predentine?
ADJ - 15 000 - 20 000
Pre dentine - 45 000 - 65 000
(more tubules in pre dentine )
what is the difference in tubule diameter in ADJ and pre dentine?
ADJ - 0.5-1.0 microns
Predentine - 2.0-3.0 microns
what is the difference in tubule distance apart (microns) in ADJ and pre dentine?
ADJ - 15 microns
Predentine - 6 microns
what is the difference in % of surface occupied by tubules in ADJ and pre dentine?
ADJ - 4%
Predentine - 28%
Deep dentine is more …..?
- more porous
- wetter
What are the curvatures in dentine?
- primary curvatures - sigmoid
- secondary curvatures - wiggle lines
where are the curvatures more sigmoid?
- in the crown
- less nearer the root
Give 3 examples of what could be found in a cross section of a tubule.
- no cell process just dentinal fluid
- odontoblast process
- odontoblast process and nerves
How much does the odontoblast process extend in dentine?
LIKELY extends approximately 1/3 the way through dentine
what are the percentages of tubules containing nerves in pre-dentine?
pulp horn - 27%-85%
cervical margin - 7%
root- 7%
what are the percentages of tubules containing nerves in the inner 1/3?
pulp horn - 10%
cervical margin- 2%
root- 0%
what are the percentages of tubules containing nerves in the outer 2/3?
pulp horn - 0%
cervical margin - 0%
root - 0%
Give a summary of nerves in dentine.
- Dentine is sparsely innervated
- Most nerves in pre-dentine/inner dentine in pulp horns
- Few at cervical margin – clinically a sensitive area
what are the 3 ways to classify dentine?
- mantle or circumpulpal
- Primary , secondary or tertiary (used clinically)
- Intertubular or peri- (or intra-) tubular dentine
what is mantle and circumpulpal dentine?
- mantle - first formed dentine
- circumpulpal dentine - everywhere else
what is primary, secondary and tertiary dentine?
- Primary - formed during tooth development (up to root completion)
- Secondary - formed after root completion , forms slowly throughout life of the tooth
- Tertiary - response to pulp insult
what happens to the pulp volume with age and what problems can arise with this?
- decreases
- endodontic access problems
what is the stimulus for tertiary dentine production?
-caries
what is tertiary dentine under stimulus?
localised
what is the reactionary reaction to produce tertiary dentine?
- uses existing odontoblasts
- slow formation
what is the reparative reaction to produce tertiary dentine?
- existing odontoblasts destroyed
- recruit newly differentiated “odontoblasts”
- rapid formation
- poor structure
what is the function of tertiary dentine?
remove pulp from stimulus
what is peri-tubular (intra -tubular dentine?
- around tubule
- highly mineralised (40% more)
what is inter-tubular ?
between tubules
what do the incremental lines of von ebner show?
the position of the odontoblasts at different times during development
what is the coincidence of secondary curvatures?
Contour line of Owen
what is interlobular dentine?
failure of calcospherite fusion
what is the appearance of the granular layer of tomes?
surface of dots, looks black, gritty
what are the possible reason for the granular layer of tomes?
- spaces
- looped/expamded tubules?
what are the age changes of secondary dentine?
Translucent sclerotic dentine:
– Tubules occluded with calcified material
– Progresses cervically from apex
– Forensics – age teeth
– Clinical:
• More peritubular dentine
• Root less flexible – fracture risk for extraction
what are the dentine changes in response to insult (tertiary)?
Sclerosis: – Tubules blocked off – Appears transparent – Nature of material in tubule? • ? peritubular dentine • ? Not formed by odontoblast • ? Mineralisation of odontoblast process? • ? Precipitate of calcium phosphate
what are dead tracts? (dentine changes in response to insult)
- odontoblasts die
- empty tubules sealed with reparative tertiary dentine
- appear dark
- can occur under normal cusp tips- odontoblast overcrowding
what is the result of dentinogenesis imperfecta?
- Primary and permanent dentitions
- Bulbous crowns
- Short roots
- Teeth translucent - grey –> brown/blue colour
- Pulp space rapidly obliterated
- Enamel poorly supported by dentine
