oral biology

Question 1

A. Diagram A represents a canine tooth in which the cusp has incisal tooth wear.

Please identify the tooth structures/components that are coloured: red, yellow, green and purple.
(4 Marks)

Answer 1

• Red – primary dentine
• Yellow – secondary dentine
• Green – tertiary dentine
• Purple – cellular cementum

Question 2

While looking under the microscope to a ground section what artifacts are likely to be found within the blue box (under the area of incisal wear)?
(1 Mark)

Answer 2

dead tracts

Question 3

Box B represents an enlarged view of the cervical region of the tooth in Diagram A.

What do the brown lines represent and how may they affect the appearance of the tooth?

Answer 3

Primary curvature of the dentinal tubules
The more tubules the more opaque
As enamel is translucent the shade of the dentine is what gives the tooth its colour. This can cause the enamel to appear yellow

Question 4

Dentinal tubules vary in density and diameter from the ADJ towards the pulp. Describe these changes. (2 marks)

Answer 4

Dentine tubules closer to the ADJ have a lower density and have a larger diameter = immature dentine

middle = density increases and diameter decreases

pulpal region = density is the highest but diameter is the smallest

Question 5

Why would it be difficult to bond to this type of dentine?

Answer 5

1. Carious dentine has a lower hardness and presence of mineral deposits in the tubules
2. This makes it difficult to produce the hybrid layer as there are denatured collagen fibres
3. Without a sufficient hydrid layer in place, bond strength will be significantly weaker

Question 6

how would we overcome hybrid layer problem?

Answer 6

RMGI: Remineralisation through F- release
Use self-etching technique to penetrate & incorporate the smear layer

Question 7

Micrograph of hybrid layer asking to label: resin tags, hybrid layer, composite restoration

Answer 7

1. Hybrid layer can be seen overlying dentine
2. Resin tags: resin that has permeated down tubules (micro mechanical retention)

Question 8

which of the dental tissues is not derived from the embryonic neural crest (ectomesenchyme)?

Answer 8

enamel

(it’s derived from epithelium)

Question 9

which dentine is laid in response to excessive cusp wear?

Answer 9

tertiary dentine

Question 10

in addition to odonblast, which structure is likely to be present within a dental tubule?

Answer 10

unmyelinated nerve

Question 11

main characteristics of cellular cementum

Answer 11

presents on the apical part of the root

Question 12

what is hybrid layer?

Answer 12

The term “hybrid layer” refers to a layer of dentin that has been modified by the application of an adhesive material.

acid-etch and bond

Question 13

what is smear layer?

Answer 13

bacterial debris that plug the dentine holes

has to be removed by acid etching