Histology Of Enamel And Dentine Caries

Question 1

How thick is enamel at its thickest?

Answer 1

2.5mm - cusps and incisal edges

Can be up to 1.3mm lateral surfaces

Question 2

Where is enamel thinnest?

Answer 2

Cervical margin

Question 3

In longitudinal section where are the prisms in relation to the ADJ?

Answer 3

Perpendicular

Question 4

What is the periodicity of the daily cross straitions?

Answer 4

5um

Question 5

Which lined are superimposed onto the daily cross striations?

Answer 5

(Brown) striae of retzius

Question 6

Why is the translucent zone translucent?

Answer 6

Takes up the imbibing fluid into the mostly uniformly sized pores produced by the early stages of acid dissolution

Question 7

How much mineral content loss is there in the body of the white spot lesion?

Answer 7

> 20% mineral loss

Question 8

Explain why the dark zone appears the way it does

Answer 8

Some remineralisation has occurred - pores vary in size - some are small and inhibit the ingress of imbibing fluid
Light gets scattered -> dark discolouration

Question 9

Describe the content of the dark zone

Answer 9

May have relatively high protein content

Lost about 5% mineral

Question 10

What may be present in the surface zone?

Answer 10

Micro channels

Question 11

Dentine can be studied using both ground and demineralised sections. Can pulp be studied using both, if not, which one?

Answer 11

No, only demineralised sections

Question 12

Where do dentine tubules run through?

Answer 12

Pulp to outer dentine surface

Question 13

What do dentinal tubules contain?

Answer 13

Fluid and odontoblast process

Question 14

What is the primary curvature?

Answer 14

S shaped path that dentinal tubules follow

Question 15

What is the secondary curvature?

Answer 15

The more frequent wave like deviations superimposed on the primary curvature.

Question 16

Dentinal tubules can be branched, where is this the most evident?

Answer 16

At the ADJ immediately under the enamel crown

Question 17

What causes caries to spread wider than visible in enamel when it gets to dentine?

Answer 17

Arrangement of prisms around fissure

Lateral spread at ADJ

Question 18

What is sclerotic dentine a response to?

Answer 18

Ageing

Defensa mechanism in response to overlying trauma

Question 19

What is sclerotic dentine?

Answer 19

Tubules completely occluded by laying down peritubular dentine within the tubules by odontoblasts.

Question 20

Is the laying down of sclerotic dentine a fast response?

Answer 20

No, it only occurs if the progress of the lesion is slow enough to let cells fill in the tubules

Question 21

Why does a dead tract appear the way it does?

Answer 21

It gets filled with air and debris during the grinding process. (Silver/black appearance)

Question 22

What is a dead tract?

Answer 22

When ells cannot maintain or mount an ordered defense by producing sclerotic dentine -> they withdraw their cell processes leaving empty tubules

Question 23

What is reparative dentine?

Answer 23

It is produced by odontoblasts to seal dentinal tubules to prevent access to the pulp.

Question 24

If odontoblasts are killed which cells take over protecting the pulp and what do they produce?

Answer 24

Subodontoblastic cells produce non-tubular bone-like material