Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BDS3 DMS > 4 - Investment materials > Flashcards

4 - Investment materials Flashcards

1
Q

What are investment materials used for?

A

Used to cast alloy components

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How are components made?

A
  • wax pattern made (of component)
  • investment material poured around wax
  • wax eliminated
  • alloy is forced into mould cavity under pressure via sprues
  • component is deinvested
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the different investment materials?

A
  • dental stone or plaster
  • gypsum bonded materials
  • phosphate bonded materials
  • silica bonded materials
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What type of investment material is used to cast acrylic dentures?

A

Dental stone or plaster

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What type of investment material is used to cast base metals / cast ceramics?

A

Phosphate bonded materials

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What type of investment material is used to cast base metal alloys?

A

Silica bonded materials

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What type of investment material is used to cast gold casting alloys?

A

Gypsum bonded materials

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is required from an investment material?

A
  • expansion, compensate for cooling shrinkage of alloy
  • porous, allows for the escape of trapped gases (chemically stable)
  • strong at both room temp and casting temp
  • smooth surface for easy finishing
  • easy handling and removal from the cast
  • inexpensive as destroyed after one use
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the typical contraction by volume of gold alloys from melting point to room temp?

A

1.4%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the typical contraction by volume of NiCr alloys from melting point to room temp?

A

2%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the typical contraction by volume of CoCr alloys from melting point to room temp?

A

2.3%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the composition of gypsum bonded investment material?

A
  • mixed with water
  • silica
  • calcium sulphate hemihydrate
  • reducing agent for oxides
  • boric acid, NaCl
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the function of boric acid in gypsum bonded investment material?

A
  • control setting times
  • inhibit heating shrinkage
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is hygroscopic expansion?

A
  • not fully understood
  • water molecules are attracted between crystals, forcing crystals apart
  • increases expansion x5
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What factors increase hygroscopic expansion?

A
  • lower powder/water ratio
  • increased silica content
  • higher water temperature
  • longer immersion time
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the composition of phosphate bonded investment material?

A

Powder
- silica
- magnetism oxide
- ammonium phosphate

Liquid
- water OR colloidal silica

17
Q

What is the function of colloidal silica solution?

A
  • increases strength
  • gives hygroscopic expansion
18
Q

What is the composition of silica investment material?

A
  • ethylsilicate
  • dilute hydrochloric acid
  • industrial spirit
19
Q

What are the two classes of investment material?

A

Binder
- gypsum
- phosphate

Refractory
- silica

BDS3 DMS (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions