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Restorative > Gypsum > Flashcards

Flashcards in Gypsum Deck (13):
0

What is a model?

Cast dimensionally accurate reproduction in a positive form of areas of the oral cavity

1

What is a die?

Positive reproduction of a tooth from an impression that has been prepared to accept a restoration

2

What are the ideal properties of model and die materials?

Dimensionally accurate
Easy to use
Accurate reproduction of fine detail
Inert
Good strength
Inexpensive
Abrasion resistant
Good colour contrast

3

What are the model and die materials that we use?

Gypsum

4

What type of structure does model gypsum have and what is it?

Monoclinic spade lattice structure

Calcium sulphate hemihydrate

5

What are the three types of gypsum?

Beta
Alpha
Alpha modified

6

What is beta form? And what colour ?

Plaster of paris and is white

7

What is the structure of the beta form? When is it used? What properties does it have?

Large irregular orthorhombic crystals
Rudimentary procedures
Soft, short setting time, high porosity

40-50ml water to 100gms

8

What is the alpha form?

Kafir D
Dental stone
yellow and ah small regular prismatic particles

25-35ml to 100gms

9

Alpha modified is what type of gypsum?

Artificial stone coloured
Large crystals
Die for crown Nd bridge

20-35ml water to 100gms

10

Why is die stone better than dental stone?

GORE
Good colour contracts
Optimum stengh when VAccum
Reasonbly inexpensive
Excellent working time

11

What is the Setting expansion of gypsum reduced by?

Potassium sulphate
Sodium chloride
Borax

12

What is the setting time of gypsum reduces by?

Reduced :Borax postasuim citrate ans sodium chloride

Increased: more than 20% gypsum! potassium sulphate and sodium chloride