Dentine Structure Flashcards
What is dentine?
What is it made of (include percentage)
Specialised connective tissue
Hard (KHN 75)
Strong and resilient
~70% mineral - hydroxyapatite
~20% organic – collagen
What direction do the collagen fibers travel and what do they do?
- travel mainly parallel to ADJ
- Gives dentine strength
Where is the primary and secondary curvature in dentine tubules?
How far do odontoblast processes extend through dentine?
extends approximately ⅓ the way through dentine
What are the 3 ways to classify dentine?
1. Developmental:
– Mantle dentine
– Circumpulpal Dentine
2. Primary, secondary and tertiary:
– Primary dentine
– Secondary dentine
– Tertiary dentine
3. Tubule:
– Peri-tubular or intra-tubular
– Inter-tubular
What are these 2 areas of dentine?
Explain the 3 types of Dentine.
Primary dentine – Formed during tooth development – i.e. up to root completion
Secondary dentine – Formed after root completion – Forms slowly throughout life of the tooth
Tertiary dentine – Response to pulpal insult
What does secondary dentine cause over time?
Over time secondary dentine is more layed down and consequently the pulp space gets a lot smalller.
What is Tertiary Dentines function and what are the 2 types of tertiary dentine.
Function: remove pulp from stimulus
Reactionary – Uses existing odontoblasts
– Slow formation
– Tubular structure
Reparative – Existing odontoblasts destroyed
– recruit newly differentiated “odontoblasts”
– Rapid formation
– Poor structure
What are the 2 types of dentine
Peri-tubular or intra-tubular – Around tubule
– Highly mineralised (40% more)
Inter-tubular – Between tubules
label the diargram
What is The position of the odontoblasts at different times during development called?
Incremental lines of von Ebner
What is the Coincidence of secondary curvatures called?
Contour Line of Owen
what happens to dentine in Sclerosis?
Sclerosis:
– Tubules blocked off
– Appears transparent
What are Dead Tracts?
Response to instult.
Odontoblasts die
Empty tubules sealed with reparative tertiary dentine
Appear dark
Can occur under normal cusp tips – odontoblast overcrowding
What happens to dentine as age increases?
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 3 Zones of established dentine caries?
Advancing front – Zone of demineralised dentine – Acid demineralisation, no bacteria
Zone of bacterial penetration – Bacteria in tubules – Lateral spread via branched tubules – Lactobacilli
Zone of destruction – Mixed bacterial population - Destroys organic matrix
What happens to the outer superficial zone and inner deeper zone of dentine in caries?
Outer, superficial zone:
– Highly infected
– Irreversibly demineralised dentine
– Proteolytic degradation of collagen matrix
Inner, deeper zone:
– Dentine has been reversibly attacked
– Collagen matrix not severely damaged
– Minimally infected
– Potential for repair
What is the importance of the hybrid layer?
Over-drying of etched dentine results in collapse of the collagen layer
this results in reduced bond strengths
WET BONDING
