Dentine

Question 1

What are the physical properties of dentine?

Answer 1

• harder than bone, softer than enamel
• cannot withstand masticatory forces
• permeable
• compressive

Question 2

What are the chemical properties of dentine?

Answer 2

Mineralised connective tissue
Inorganic:
- hydroxyapatite crystals (more impurities than enamel)
Organic:
- collagen I (embedded within mineralised matrix)
- Non-collagenous proteins (dentine phosphoproteins)

Question 3

How is dentine different to enamel.
(-structural
-physical
-chemical)

Answer 3

• dentine has dentinal tubules, enamel has prismatic microstructure of hydroxyapatite crystals arranged in rods/prisms
• dentine is less mineralised
• dentine has collagen I

Question 4

What does dentine consist of mainly…

Answer 4

Hydroxyapatite crystals in an organic fibrillar matrix

Question 5

What are the constituent of the organic matrix (+specifics of fibrils included) in dentine .

Answer 5

• collagen type 1

Question 6

What is tubular dentine?

Answer 6

• tooth structure that consists of dentinal tubules

Question 7

What is peritubular dentine? (what can this cause)

Answer 7

• dentine deposited on walls of dentinal tubule in maturation
• narrowing of lumen

Question 8

What is intertubular dentine?

Answer 8

Dentine located between dentinal tubules

Question 9

How can changes in dentinal tubules affect dentine permeability?

Answer 9

• tubule diameter (increased deposition of peritubular dentine can limit permeability)

Question 10

Explain the mineralisation process of dentine.

Answer 10

1. Odontoblast process deposit unmineralised pre-dentine and organic matrix
2. Mineralisation occurs fast after deposition
3. Calcium and phosphorus ions from surrounding fluid in the pulp combine to form hydroxyapatite crystals
4. Nucleation of hydroxyapatite crystals
5. As mineralisation progresses, dentinal tubules form

Question 11

Explain what calcospherites are and their formation.

Answer 11

• spherical hydroxyapatite formed during the mineralisation of dentine
• CHECK DISCUSSION BOARD

Question 12

What is sclerotic dentine, and when may it be produced?

Answer 12

• dentine that contains dentinal tubules that are completely full of peritubular dentine
• appears transparent
  -in response to ‘insult’

Question 13

How can translucent dentine be used to estimate age?

Answer 13

-translucent dentine deposited with age
-the more transparent the dentine looks, the older the patient is

Question 14

Where is Circumpulpal dentine located and what’s a characteristic of it.

Answer 14

• the bulk of dentine between predentine and ADJ
• uniform structure

Question 15

What’s the role of odontoblasts in dentine formation + maintenance?

Answer 15

• odontoblast processes in odontoblasts secrete organic matrix (predentine)
• mineralisation of predentine occurs
• secondary dentine is deposited throughout life

Question 16

What are the 2 types of tertiary dentine and when are they deposited?

Answer 16

Reactionary (some cells not died so they produce reparative dentine)
Reparative (all cells have died, stem cells differentiate into ‘odontoblast-like-cells’ and produce reparative dentine)

Question 17

Explain the hydrodynamic theory.

Answer 17

• stimulus triggers flow of fluid (dentinal fluid) within dentinal tubules
• the movement depolarises nerve endings

Question 18

Why is dentine more susceptible to acid dissolution than enamel?

Answer 18

• dentine is softer
• dentine has lower mineral content
• dentinal tubules allow penetration of acid

Question 19

Why does caries spread faster in dentine than enamel?

Answer 19

• lower mineral content
• dentinal tubules allow penetration of acid

Question 20

Where’s the hyaline layer

Answer 20

Between Circumpulpal dentine and cementum