Deck 9: Model and Die Materials

Question 1

Which of the following types of gypsum products is also known as die stone?

A) Impression plaster
B) Model plaster
C) Dental stone
D) High-strength/low-expansion dental stone
E) High-strength/high-expansion dental stone

Answer 1

High-strength/low-expansion dental stone

Question 2

_____ are highly accurate replicas of a single tooth and generally are used to make metal crowns or inlays.

A) Models
B) Casts
C) Dies
D) A and C
E) B and C

Answer 2

Dies

Question 3

When a model or die is wet,its compressive and tensile strength is approximately _____ its strength when dry.

A) 4 times
B) twice
C) one-half
D) one-quarter
E) one-sixteenth

Answer 3

one-half

Question 4

Orthodontic plaster is a mixture of:

A) impression plaster and model plaster.
B) model plaster and dental stone.
C) impression plaster and dental stone.
D) high-strength/low-expansion and high-strength/high-expansion dental stone.

Question 5

The _____ and _____ dense the crystal of the hemihydrate,the less excess water required to get a workable mass.

A) larger; more
B) larger; less
C) smaller; more
D) smaller; less

Question 6

Which form of dental gypsum product is created by boiling gypsum in a 30% solution of calcium chloride?

A) Model plaster
B) Dental stone
C) High-strength dental stone
D) A and B
E) B and C

Question 7

As compressive strength of gypsum materials increases,_____ increases.

A) both hardness and abrasion resistance
B) hardness but not abrasion resistance
C) abrasion resistance but not hardness
D) neither hardness nor abrasion resistance

Question 8

When gypsum is mixed by hand,the mass is stirred with a spatula at a rate of about _____ revolution(s)per second for _____.

A) five; about 5 minutes
B) two; about 2 minutes
C) two; about 1 minute
D) one; about 2 minutes
E) one; 30 seconds

Question 9

Gypsum model and die materials exhibit _____ in contrast to epoxy model and die materials.

A) excellent abrasion resistance
B) excellent compatibility with impression materials
C) slight expansion
D) both A and B
E) both B and C

Question 10

When powder and water are added to the mixing bowl:

A) powder should be added first.
B) water should be added first.
C) the second material added should be sprinkled in slowly over a period of about 30 seconds.
D) both A and C.
E) both B and C.

Question 11

If the temperature of the water used to mix gypsum materials is raised up to body temperature (37.5° C),the setting time decreases.However,if water temperature is raised above 37.5° C,the setting time will increase.

A) Both statements are true.
B) Both statements are false.
C) The first statement is true; the second statement is false.
D) The first statement is false; the second statement is true.

Question 12

Which of the following statements is true of the production of dental stone?

A) It is produced by heating gypsum in an open kettle.
B) The hemihydrate produced is b-calcium sulfate hemihydrate.
C) The hemihydrate produced is a-calcium sulfate hemihydrate.
D) A and B are true statements.
E) A and C are true statements.

Question 13

Clinically,the best way to determine the final setting time is:

A) loss of surface gloss.
B) when the material can no longer be poured.
C) when the conversion of hemihydrate to dihydrate is complete.
D) dissipation of the heat of reaction.

Question 14

Which of the following materials will accelerate the setting reaction of gypsum products?

A) Blood
B) Saliva
C) Agar
D) Terra alba
E) Unset alginate

Question 15

Which of the following types of dental stone and dental plaster requires the least amount of excess water?

A) Model plaster
B) Dental stone
C) High-strength dental stone

Question 16

Using excessive water to prepare gypsum materials will result in:

A) a reduction in the setting time.
B) a reduction in strength.
C) increased setting expansion.
D) A, B, and C.
E) A and C.

Question 17

Which of the following chemicals is an effective accelerator for gypsum materials?

A) Calcium sulfate
B) Potassium sulfate
C) Borax
D) B-calcium sulfate hemihydrate
E) A-calcium sulfate hemihydrate

Question 18

Accelerators are chemicals that _____ the rate of setting and _____ the time of setting.

A) increase; increase
B) increase; decrease
C) decrease; increase
D) decrease; decrease

Question 19

Which of the following statements is true of the compressive strengths of gypsum materials?

A) Die stone has the lowest compressive strength, because it has the least excess water.
B) Die stone has the lowest compressive strength, because it has the most excess water.
C) Die stone is almost 4 times as strong in compression as plaster, because the excess water is minimized.
D) Die stone is almost 4 times as strong in compression as plaster, because the excess water is maximized.

Question 20

Which of the following model and die materials are derived from the mineral gypsum?

A) Model plaster
B) Dental stone
C) High-strength dental stone
D) A, B, and C
E) A and C

Question 21

The inherent roughness limits the ability of gypsum materials to capture the finest details of impressions.Reproduction of detail is sufficient for most applications.

A) Statement 1 is correct; statement 2 is correct.
B) Statement 1 is correct; statement 2 is incorrect.
C) Statement 1 is incorrect; statement 2 is correct.
D) Statement 1 is incorrect; statement 2 is incorrect.

Question 22

Proper wetting occurs when gypsum is poured against a _____-based impression material such as _____.

A) water; alginate
B) water; addition silicone
C) non-water; alginate
D) non-water; addition silicone

Question 23

The final setting time is defined as:

A) the point where the gypsum can be removed without fracture.
B) the point where the gypsum can be removed without distortion.
C) the point where the exothermic reaction is complete.
D) all of the above.
E) only A and B.

Question 24

Hardness and abrasion resistance is especially important for:

A) study models.
B) orthodontic models.
C) dies.
D) casts.

Question 25

Water-powder ratio is defined as the amount of water in _____ added to the amount of powder in _____.

A) ounces; ounces
B) milliliters; ounces
C) ounces; grams
D) milliliters; grams

Question 26

When the alginate dries out before it is poured:

A) the alginate will rob the gypsum mix of some of its water.
B) the edges of the alginate may become hard and inflexible.
C) the impression will be distorted.
D) A, B, and C are correct.
E) A and C are correct.

Question 27

Casts of teeth are used to make:

A) crowns.
B) inlays.
C) retainers.
D) all of the above.

Question 28

Epoxy materials are compatible with most of the elastomeric impression materials.Epoxy materials can be used with alginates.

A) Statement 1 is correct; statement 2 is correct.
B) Statement 1 is correct; statement 2 is incorrect.
C) Statement 1 is incorrect; statement 2 is correct.
D) Statement 1 is incorrect; statement 2 is incorrect.

Question 29

The purpose of the vibrating table is to:

A) ensure a smooth mix of the materials.
B) help remove any bubbles that formed during mixing.
C) initiate the setting reaction.
D) wet the gypsum powder particles.

Question 30

If a 2% solution of borax is added to the gypsum powder,what will be the result? The setting time will be:

A) reduced significantly.
B) reduced slightly.
C) extended significantly.
D) extended slightly.

Question 31

The impression should not be removed from the gypsum for _____ minutes.

A) 3 to 5
B) 5 to 10
C) 10 to 20
D) 20 to 40
E) 45 to 60

Question 32

If gypsum materials are not adequately spatulated,_____ suffers.

A) accuracy
B) dimensional change
C) strength
D) abrasion resistance

Question 33

Which of the following statements is(are)correct about making models,casts,and dies?

A) Fine detail is not significant.
B) Gypsums are not dimensionally stable.
C) The material does not need to be strong.
D) A, B, and C are all correct.
E) A, B, and C are all incorrect.

Question 34

Dies of epoxy for use in fabrication of crowns,bridges,and inlays can be poured into alginate.Epoxy dies are tougher and more abrasion resistant than high-strength stone dies,and they are more accurate and stable dimensionally.

A) Statement 1 is correct; statement 2 is correct.
B) Statement 1 is correct; statement 2 is incorrect.
C) Statement 1 is incorrect; statement 2 is correct.
D) Statement 1 is incorrect; statement 2 is incorrect.

Question 35

High-strength stone requires the least amount of excess water,because the crystals are:

A) large and dense.
B) large and sparse.
C) small and dense.
D) small and sparse.

Question 36

The initial setting time for gypsum is defined as the time the:

A) powder is added to the water until mixing is complete.
B) powder is added to the water until the pour is complete.
C) pour begins until the pour is complete.
D) powder is added to the water until the material cannot be used.

Question 37

Which of the following statements is true regarding disinfection of a gypsum model?

A) The model may be sterilized in an autoclave.
B) Disinfecting the impression rather than the model is preferable.
C) Disinfecting the model rather than the impression is preferable.
D) A and B are true statements.
E) A and C are true statements.

Question 38

A hemihydrate will not set if the:

A) body temperature is above 37.5°
B) body temperature is below 37.5°
C) mixing water reaches 100° C.

Question 39

Which of the following statements is true of the handling of an alginate impression?

A) The heat produced is the result of an endothermic reaction.
B) An alginate impression should be rinsed completely and disinfected after pouring.
C) Any residual water in low places of the impression should not be removed.
D) The poured impression may be kept moist by storing it in a humid environment.