DM.7

Question 1

What are the 3 ways metals and alloys are shaped in dentistry?

Answer 1

1. casting
2. cold working
3. amalgamation

Question 2

Why is casting quite expensive?

Answer 2

energy needed to pour/force material into mould AND finish by polishing

Question 3

give 4 examples of cold working used fro shaping metals and alloys:

Answer 3

forging, rolling, drawing and milling

Question 4

What is amalgamation?

Answer 4

reaction with mercury, moulding of paste

Question 5

describe a temperature time graph of liquid metal cooling?

Answer 5

a) cooling occurs at constant rate, structure: ions get closer other and move less
b) temperature constant as solidification occurs at MpT, structure: latent heat of crystallisation, as energy goes in to making bounds forming nuclei (where grains grow from), grains forms are equixed
c) solid now cools at constant temperture,

Question 6

What does equixed mean?

Answer 6

(same dimension in all directions)

Question 7

How can you increase the number of nuclei of grains and thus the number of grains?

Answer 7

through seeding, adding another metal

Question 8

Dendrites are ….

Answer 8

??

Question 9

Describe a) range of order of a lattice:

Answer 9

long range order

Question 10

What are he 3 cubic structures:

put them in order from least to most packed

Answer 10

1. simple cubic
2. body centred cubic
3. face centred cubic

Question 11

What are the types of defect you can get in crystals?

Answer 11

point and line defects

Question 12

what are the different point defects?

Answer 12

• Impurities

* Vacancies (a hole)

Question 13

what are the different line defects?

Answer 13

• Dislocations
• Edge dislocations (shown in bottom right image)
• Screw dislocations (rotation issue)

Question 14

equixed grains formed on cooling will contain defects called…

Answer 14

crystal defects