Deck 15: Gypsum Products

Question 1

Which of the following dental gypsum products will require the least water for mixing and will have the highest final density?

A) Impression plaster (Type I)
B) Model plaster (Type II)
C) Dental stone (Type III)
D) Dental stone, high strength (Type IV)

Answer 1

Dental stone, high strength (Type IV)

Question 2

Which of the following statements is true concerning the mixing of plaster and stone materials?

A) The measured amount of powder is placed into the mixing bowl and the water is slowly sifted into the powder.
B) The measured amount of powder is placed into the mixing bowl and the water is dumped into the powder.
C) The measured amount of water is placed into the mixing bowl and the powder is slowly sifted into the water.
D) The measured amount of water is placed into the mixing bowl and the powder is dumped into the water.

Answer 2

The measured amount of water is placed into the mixing bowl and the powder is slowly sifted into the water.

Question 3

When working models for cast restorations are being made, a die of high-strength stone (Type IV) is often poured with a base and adjacent teeth of Type __ stone.

A) I
B) II
C) III
D) V

Answer 3

III

Question 4

The ______________________________ the particles of gypsum powder are, the weaker and less resistant to abrasion is the final product.

A) smaller, more regular, and porous
B) smaller, more irregular, and denser
C) larger, more irregular, and porous
D) larger, more regular, and denser

Question 5

___________ is a material able to withstand the high heat and stress produced when molten metal is forced into molds to form indirect restorations.

A) Model plaster
B) Dental investment
C) Dental stone
D) Die stone

Question 6

Model plaster has a water-to-powder ratio of approximately __ (ml/g).

A) 0.15
B) 0.45
C) 1.00
D) 2.50

Question 7

Which of the following gypsum products is ideal for making full or partial denture models, orthodontic models, and casts requiring higher strength and abrasive resistance?

A) Impression plaster (Type I)
B) Model plaster (Type II)
C) Dental stone (Type III)
D) Dental stone, high strength (Type IV)

Question 8

Which of the following is true regarding trimming of models with a model trimmer?

A) Bases and anatomic portions should be soaked for 5 to 10 minutes before trimming.
B) The casts should be trimmed so that proportionately the base makes up one third and the anatomic portion two thirds of the total depth.
C) The occlusal plane should be perpendicular with the base.
D) The anterior portion of both the maxillary and mandibular arch models should be trimmed to a point at the midline.

Question 9

An increase in spatulation time and rate will ________ the setting time and _______ the rate of setting expansion.

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

Question 10

Which of the following statements is true regarding dimensional accuracy of gypsum products?

A) Plaster has the least amount of setting expansion.
B) High-strength stones have the least amount of setting expansion.
C) Plaster has the least amount of setting contraction.
D) High-strength stones have the least amount of setting contraction.

Question 11

Which of the following is true concerning the chemical properties of gypsum materials?

A) Chemically, the mineral gypsum is a hemihydrate of calcium carbonate.
B) To form the raw material into a powder, the manufacturer heats it and adds water.
C) When the dihydrate is again mixed with water, a product with a viscosity capable of flowing is produced.
D) The amount of water required to mix the calcium sulfate hemihydrate is greater than the amount required for the chemical reaction.

Question 12

Which of the following impression materials generally forms the best surface detail with gypsum products?

A) Reversible hydrocolloid
B) Irreversible hydrocolloid
C) Addition silicone
D) Polysulfide rubber base

Question 13

Which of the following will accelerate setting of gypsum products?

A) Alginate
B) Set gypsum particles
C) Blood
D) Saliva

Question 14

An increase in the recommended water-to-powder ratio will result in a ______________________ accurate model.

A) stronger, more
B) stronger, less
C) weaker, more
D) weaker, less

Question 15

For regular-set gypsum products, the initial set occurs within ________ minutes from the beginning of the mix.

A) 1 to 2
B) 3 to 5
C) 7 to 9
D) 12 to 14

Question 16

Loss of gloss indicates that freshly mixed gypsum has reached its:

A) beginning of the working time
B) final compressive strength
C) initial set
D) final set

Question 17

$\beta$ -Hemihydrate is commonly used for:

A) diagnostic models
B) working casts
C) die stone
D) dental investment

Question 18

When proportioning gypsum products, the water should be measured with a graduated cylinder and the powder should be:

A) mixed by guess and by golly
B) weighed on a scale
C) measured with the use of scoops
D) measured with a graduated cylinder as well

Question 19

Which of the following is true of the double-pour method for fabricating and trimming diagnostic/working casts?

A) After the impression is poured, the remaining material is used for the base.
B) The material in the inverted impression may slump away from the impression, causing distortion of the cast or trapping or air voids.
C) This technique involves two separate mixes.
D) One mix of gypsum is produced to pour the anatomic and art portions of the cast.

Question 20

Increased porosity of the gypsum particles makes it necessary to use ________ water to convert the ____________________ when mixing gypsum products.

A) more; hemihydrate particles back to dihydrate particles
B) less; hemihydrate particles back to dihydrate particles
C) more; dihydrate particles back to hemihydrate particles
D) less; dihydrate particles back to hemihydrate particles

Question 21

Match the items with the correct description below.
Diagnostic casts

A)Replicas of the prepared teeth that are generally removable from the working cast
B)Hard replicas of hard and soft tissues of the patient's oral cavity made from gypsum products
C)Casts generally made from dental plaster or stone and used for patient education, treatment planning, and tracking of the progress of treatment

Question 22

The ______ water is mixed with the powder, the ______ the cast will be.

A) more; stronger
B) more; weaker
C) less; stronger
D) less; weaker
E) Either B or C

Question 23

List and describe the use of the different types of gypsum products used in dentistry.

Question 24

Manufacturers recommend that models be pulled:

A) about 1 hour after the pour
B) after the exothermic reaction cools
C) when the surface appears firm
D) within 24 hours of the pour

Question 25

When mixing plaster to pour up an impression, one must:

A) mix the material slowly to alter setting time
B) sift the powder into the water to wet completely
C) wait for the glossy appearance to fade before pouring
D) leave the material with some lumps to vibrate out

Question 26

Which of the following would not alter the setting time of gypsum?

A) Changing the powder-to-water ratio
B) Changing the water temperature
C) Using a mechanical mixer
D) Adding accelerator or retardants

Question 27

Once the initial set of the stone has occurred, the material:

A) will continue to flow until set
B) will be at its strongest point
C) will lose its glossy appearance
D) should not be disturbed at all

Question 28

Heat is a by-product of a chemical reaction within the hemihydrates. This is known as an _______reaction.

A) ectopic
B) endothermic
C) exothermic
D) explicit

Question 29

Match the items with the correct description below.
Dies

A)Replicas of the prepared teeth that are generally removable from the working cast
B)Hard replicas of hard and soft tissues of the patient's oral cavity made from gypsum products
C)Casts generally made from dental plaster or stone and used for patient education, treatment planning, and tracking of the progress of treatment

Question 30

The base of the poured cast is referred to as the _______ and should be approximately one third of the overall height of the cast.

A) anatomic form
B) diagnostic model
C) art form
D) working model

Question 31

Match the items with the correct description below.
Models

A)Replicas of the prepared teeth that are generally removable from the working cast
B)Hard replicas of hard and soft tissues of the patient's oral cavity made from gypsum products
C)Casts generally made from dental plaster or stone and used for patient education, treatment planning, and tracking of the progress of treatment

Question 32

Match the items with the correct description below.
Study models

A)Replicas of the prepared teeth that are generally removable from the working cast
B)Hard replicas of hard and soft tissues of the patient's oral cavity made from gypsum products
C)Casts generally made from dental plaster or stone and used for patient education, treatment planning, and tracking of the progress of treatment

Question 33

A stone cast poured from an impression is a/an _________ reproduction.

A) negative
B) positive
C) complete
D) incomplete

Question 34

When stone is mixed with silica, this is referred to as ______.

A) die stone
B) plaster
C) hemihydrates
D) investment

Question 35

Mechanical spatulation would be used to:

A) provide an even mix
B) reduce air bubbles
C) improve mix accuracy
D) All of the above

Question 36

Match the items with the correct description below.
Casts

A)Replicas of the prepared teeth that are generally removable from the working cast
B)Hard replicas of hard and soft tissues of the patient's oral cavity made from gypsum products
C)Casts generally made from dental plaster or stone and used for patient education, treatment planning, and tracking of the progress of treatment