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DENT MAT PRELIMS > QUIZ 1 - GYPSUM > Flashcards

QUIZ 1 - GYPSUM Flashcards

1
Q

What is the chemical name and formula of Gypsum?

A

Calcium Sulfate Dihydrate, CaSO4+2H2O

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2
Q

This is a study purpose cast which has a positive likeness of an oral cavity.

A

Model

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3
Q

This is a model that has a positive replica of an oral cavity.

A

Cast

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4
Q

This is a negative replica of an oral cavity.

A

Impression

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5
Q

This is used to make a positive replica of a PREPARED tooth.

A

Die Stone

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6
Q

A replica of a prepped tooth is made out of 4 materials, what are these?

A

Gypsum products, Epoxy resins, metal, refractive materials

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7
Q

This is the β (beta) form of calcium hemihydrate.

A

Dental Plaster

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8
Q

This is the α (alpha) form of calcium hemihydrate.

A

Dental Stone

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9
Q

What do you call the ratio in which water is mixed with the hemihydrate.

A

W/P Ratio (Water to Powder Ratio)

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10
Q

Time from addition of the powder to water until the mixing is complete.

A

Mixing Time

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11
Q

The duration between start of mix & point where material hardens.

A

Setting Time

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12
Q

Time from start to mix to the point where the consistency of the mix is no longer acceptable for usage of intended purpose.

A

Working Time (Dito na nagfufunction yung material.)

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13
Q

Impurities added to gypsum product (mixture) which reduces the setting time (bibilis)

A

Accelerators

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14
Q

Impurities added to gypsum products that enhance the setting time (pinapabagal tumigas)

A

Retarders

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15
Q

The process of heating gypsum for the manufacture of plaster

A

Calcination

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16
Q

In order for the dihydrate to become hemihydrate, it will go through the process of ______.

A

Calcination

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17
Q

Heating ground gypsum in an open kettle

A

Dry Calcination

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18
Q

Temperature of Dry Calcination

A

115°C

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19
Q

Product of Dry Calcination

A

Dental Plaster (β calcium hemihydrate)

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20
Q

Heating gypsum under pressure and in the presence of water vapor.

A

Wet Calcination

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21
Q

Temperature of Wet Calcination

A

125°C

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22
Q

Product of Wet Calcination

A

Dental stone (α calcium hemihydrate)

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23
Q

What is the process of boiling gypsum in 30% solution of Calcium Chloride called?

A

Dehydration by boiling chemicals

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24
Q

What is the product of Dehydration by boiling chemicals?

A

High Strength Dental Stone

25
Q

Calcination:
CaSO4 + 2H2O —> _______

A

CaSO4 + 1/2H2O

26
Q

What is the reaction of the plaster upon mixed with water?

A

It becomes exothermic (umiinit)

27
Q

What do you call the time when there is a little reaction or a little to no rise in temperature?

A

Induction Period

28
Q

Uses of Gypsum

A

General: For construction purposes

Orthopedic: For preparation of casts

Dentistry:
- Impression Plaster
- To mount the cast on the articulator
- For bite registration
- Dental investments

29
Q

Types of Gypsum/Dental Stone Products

A

Type I - Impression Plaster
Type II - Dental Plaster
Type III - Dental Stone/Cast Stone
Type IV - Improved Dental Stone or Die Stone or High Strength Stone
Type V - Dental Stone, High Strength, High Expansion

30
Q

Use of Type I Plaster

A

For making primary impression of edentulous oral cavity in complete denture fabrication.

31
Q

Type I Plaster is composed of?

A

Plaster of Paris (colored and flavored)

32
Q

Function of adding few modifiers to Type I Plaster

A

To regulate the setting time and expansion

33
Q

Purpose of Type II Plaster

A

To produce study cast or primary casts.
To fill flasks during complete denture fabrication.

34
Q

W/P ration of Type II Plaster

A

45:100

35
Q

Shape of Type II Plaster

A

Irregular orthorhombic crystals

36
Q

Purpose of Type III Dental Stone

A

It is used in making MASTER CAST.

37
Q

Shape of Type III Dental Stone

A

Rods and prisms

38
Q

W/P Ratio of Type III Dental Stone

A

30:100

39
Q

Type IV Dental Stone is also known as ______?

A

Die Stone and High Strength Stone

40
Q

Shape of Type IV Dental Stone

A

Cuboidal Crystals

41
Q

W/P Ratio of Type IV Dental Stone

A

19-24:100

42
Q

W/P Ratio of Type V Dental Stone

A

18-22:100

43
Q

Two Types of Setting Expansion

A

Normal Setting Expansion
Hygroscopic Setting Expansion

44
Q

Refers to the setting expansion when a gypsum product is allowed to expand in air (when placed on table or dry environment).

A

Normal Setting Expansion

45
Q

Refers to the expansion of the gypsum products what it is allowed to set, immersed in water

A

Hygroscopic Setting Expansion

46
Q

Tests for Setting of Gypsum Products

A
  1. Loss of Gloss Test
  2. Gilmore’s Test
  3. Vicat Needle Test for Setting Time
  4. Ready for Use Criterion
47
Q

The strength of a stone is inversely proportional to the ______.

A

W/P Ratio

48
Q

TRUE or FALSE: It is better to keep the amount of water as low as possible.

A

TRUE

49
Q

What instrument must be used in measuring water.

A

Accurate Graduated Cylinder

50
Q

What must be used for measuring the powder?

Note: SHOULD NOT BE MEASURED USING SCOOP

A

Proper Weighing Balance

51
Q

Why must you not mix the plaster in full circle?

A

The plaster will incorporate bubbles which will make the cast brittle and prone to breakage.

52
Q

If the mixing has to be done by hand, the bowl must be (1)____, (2)____, and (3)_____?

A

parabolic, smooth and abrasion resistant

53
Q

Spatula should have a (1)____ and (2)____.

A

stiff blade and a convenient handle

54
Q

What is the purpose of hot water?

A

It reduces mixing time

55
Q

Example of Accelerators

A

Potassium Sulfate
Calcium Sulfate Dihydrate Crystals (From plasters that has already been set)
Salt (Not more than a pinch)

56
Q

Rate of reaction is increased when

A

The temperature is increased to body temp

(Sa bibig unang magseset kaysa sa room temp because of our body temp)

57
Q

Gypsum will not set when the temperature is

A

100°C

58
Q

Example of Retarders

A

Borax
Blood
Saliva
Agar
Alginate
Cold Water

59
Q

Why should we stir the water powder more vigorously during the mixing step?

A

To avoid air entrapments

DENT MAT PRELIMS (1 decks)

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