Dentine Structure

Question 1

What is dentine?

What is it made of (include percentage)

Answer 1

Specialised connective tissue

Hard (KHN 75)

Strong and resilient

~70% mineral - hydroxyapatite

~20% organic – collagen

Question 2

What direction do the collagen fibers travel and what do they do?

Answer 2

• travel mainly parallel to ADJ
• Gives dentine strength

Question 3

Where is the primary and secondary curvature in dentine tubules?

Answer 3

Question 4

How far do odontoblast processes extend through dentine?

Answer 4

extends approximately ⅓ the way through dentine

Question 5

What are the 3 ways to classify dentine?

Answer 5

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

Question 6

What are these 2 areas of dentine?

Answer 6

Question 7

Explain the 3 types of Dentine.

Answer 7

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

Question 8

What does secondary dentine cause over time?

Answer 8

Over time secondary dentine is more layed down and consequently the pulp space gets a lot smalller.

Question 9

What is Tertiary Dentines function and what are the 2 types of tertiary dentine.

Answer 9

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

Question 10

What are the 2 types of dentine

Answer 10

Peri-tubular or intra-tubular – Around tubule

– Highly mineralised (40% more)

Inter-tubular – Between tubules

Question 11

label the diargram

Answer 11

Question 12

What is The position of the odontoblasts at different times during development called?

Answer 12

Incremental lines of von Ebner

Question 13

What is the Coincidence of secondary curvatures called?

Answer 13

Contour Line of Owen

Question 14

what happens to dentine in Sclerosis?

Answer 14

Sclerosis:

– Tubules blocked off

– Appears transparent

Question 15

What are Dead Tracts?

Answer 15

Response to instult.

Odontoblasts die

Empty tubules sealed with reparative tertiary dentine

Appear dark

Can occur under normal cusp tips – odontoblast overcrowding

Question 16

What happens to dentine as age increases?

Answer 16

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

Question 17

What are the 3 Zones of established dentine caries?

Answer 17

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

Question 18

What happens to the outer superficial zone and inner deeper zone of dentine in caries?

Answer 18

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

Question 19

What is the importance of the hybrid layer?

Answer 19

Over-drying of etched dentine results in collapse of the collagen layer

this results in reduced bond strengths

WET BONDING