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DENT MAT PRELIMS > QUIZ 1 - GYPSUM > Flashcards

QUIZ 1 - GYPSUM Flashcards

(59 cards)

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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?

Study These Flashcards
A

High Strength Dental Stone

25
Calcination: CaSO4 + 2H2O ---> _______
CaSO4 + 1/2H2O
26
What is the reaction of the plaster upon mixed with water?
It becomes exothermic (umiinit)
27
What do you call the time when there is a little reaction or a little to no rise in temperature?
Induction Period
28
Uses of Gypsum
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
Types of Gypsum/Dental Stone Products
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
Use of Type I Plaster
For making primary impression of edentulous oral cavity in complete denture fabrication.
31
Type I Plaster is composed of?
Plaster of Paris (colored and flavored)
32
Function of adding few modifiers to Type I Plaster
To regulate the setting time and expansion
33
Purpose of Type II Plaster
To produce study cast or primary casts. To fill flasks during complete denture fabrication.
34
W/P ration of Type II Plaster
45:100
35
Shape of Type II Plaster
Irregular orthorhombic crystals
36
Purpose of Type III Dental Stone
It is used in making MASTER CAST.
37
Shape of Type III Dental Stone
Rods and prisms
38
W/P Ratio of Type III Dental Stone
30:100
39
Type IV Dental Stone is also known as ______?
Die Stone and High Strength Stone
40
Shape of Type IV Dental Stone
Cuboidal Crystals
41
W/P Ratio of Type IV Dental Stone
19-24:100
42
W/P Ratio of Type V Dental Stone
18-22:100
43
Two Types of Setting Expansion
Normal Setting Expansion Hygroscopic Setting Expansion
44
Refers to the setting expansion when a gypsum product is allowed to expand in air (when placed on table or dry environment).
Normal Setting Expansion
45
Refers to the expansion of the gypsum products what it is allowed to set, immersed in water
Hygroscopic Setting Expansion
46
Tests for Setting of Gypsum Products
1. Loss of Gloss Test 2. Gilmore's Test 3. Vicat Needle Test for Setting Time 4. Ready for Use Criterion
47
The strength of a stone is inversely proportional to the ______.
W/P Ratio
48
TRUE or FALSE: It is better to keep the amount of water as low as possible.
TRUE
49
What instrument must be used in measuring water.
Accurate Graduated Cylinder
50
What must be used for measuring the powder? Note: SHOULD NOT BE MEASURED USING SCOOP
Proper Weighing Balance
51
Why must you not mix the plaster in full circle?
The plaster will incorporate bubbles which will make the cast brittle and prone to breakage.
52
If the mixing has to be done by hand, the bowl must be (1)____, (2)____, and (3)_____?
parabolic, smooth and abrasion resistant
53
Spatula should have a (1)____ and (2)____.
stiff blade and a convenient handle
54
What is the purpose of hot water?
It reduces mixing time
55
Example of Accelerators
Potassium Sulfate Calcium Sulfate Dihydrate Crystals (From plasters that has already been set) Salt (Not more than a pinch)
56
Rate of reaction is increased when
The temperature is increased to body temp (Sa bibig unang magseset kaysa sa room temp because of our body temp)
57
Gypsum will not set when the temperature is
100°C
58
Example of Retarders
Borax Blood Saliva Agar Alginate Cold Water
59
Why should we stir the water powder more vigorously during the mixing step?
To avoid air entrapments

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