Deck 8: Impression Materials

Question 1

Alginate impressions prepared from extended storage products usually can be stored under proper conditions for up to _____ without serious dimensional changes.

A) 10 minutes
B) 1 hour
C) 1 day
D) 5 days
E) 2 weeks

Answer 1

5 days

Question 2

Which of the following is a rigid dental impression material?

A) Polyether
B) Polysulfide
C) Addition silicone
D) Zinc oxide-eugenol

Answer 2

Zinc oxide-eugenol

Question 3

Which term describes the process through which alginate gels shrink and lose water?

A) Syneresis
B) Imbibition
C) Dehydration
D) Agglutination
E) Agglomeration

Answer 3

Syneresis

Question 4

Which type of impression material is the most popular for restorative procedures?

A) Polyether
B) Polysulfide
C) Hydrocolloid
D) Addition silicone

Question 5

What is the ANSI-ADA requirement for recovery of alginate impression materials?

A) 80%
B) 85%
C) 90%
D) 95%

Question 6

What is the main disadvantage of alginate hydrocolloid impression material in contrast to an elastomeric impression?

A) Its higher cost
B) The amount of equipment necessary
C) The inflexibility of the set impression
D) Difficulty in mixing and manipulating
E) It does not transfer as much surface detail to gypsum dies.

Question 7

Measurement of dimensional changes showed that immersion of alginate impressions for _________ did not affect their clinical accuracy.

A) 10 minutes
B) 30 minutes
C) 1 hour
D) 5 days
E) 2 weeks

Question 8

Storing set alginate _____________ will result in the least dimensional change.

A) in dry air
B) under water
C) in air approaching 50% relative humidity
D) in air approaching 100% relative humidity

Question 9

What is the best method for delaying the setting of alginate?

A) Increase the water temperature.
B) Reduce the water temperature.
C) Use a thinner mix of alginate.
D) Use a thicker mix of alginate.

Question 10

The impression gives a ________ reproduction of tissue. A ________ reproduction is obtained by pouring dental stone or other suitable material into the impression and allowing it to harden.

A) negative; negative
B) positive; positive
C) negative; positive
D) positive; negative

Question 11

What is the recommended mixing time of fast-setting alginate?

A) Less than 15 seconds
B) 30 to 45 seconds
C) 1.25 minutes
D) 2 minutes

Question 12

What are the recommendations for mixing alginate?

A) Using ice water
B) Adding the powder to the water
C) Adding the water to the powder
D) Both A and B
E) Both A and C

Question 13

Alginate impression material may be referred to as which type of material?

A) Polyether
B) Addition silicone
C) Condensation silicone
D) Irreversible hydrocolloid
E) Reversible hydrocolloid

Question 14

Which of the following ingredients of alginate hydrocolloid reacts with dissolved alginate to form insoluble calcium alginate?

A) Calcium sulfate
B) Potassium sulfate
C) Sodium phosphate
D) Sodium or potassium alginate salt

Question 15

At final seating, the incisal edges and cuspal tips should be ________ the surface of the tray.

A) contacting
B) about 1 to 2 mm from
C) about 3 to 4 mm from
D) at least 6 mm from

Question 16

How is alginate hydrocolloid supplied?

A) Powder
B) Compules
C) Thixotropic gel
D) Two syringes to be mixed together
E) Two tubs as a putty system for hand kneading

Question 17

Sodium phosphate acts as a(n) ________ during the setting reaction of alginate hydrocolloid.

A) initiator
B) retarder
C) sweetener
D) accelerator
E) disinfectant

Question 18

When is alginate hydrocolloid recommended?

A) Preparation of study models
B) Impressions of cavity preparations
C) In the preparation of athletic mouth protectors
D) For A, B, and C
E) For A and C

Question 19

The ANSI-ADA specification requires no more than ____% permanent deformation when an alginate is compressed 20% for 5 seconds.

A) 2
B) 5
C) 25
D) 50
E) 95

Question 20

Higher rates of alginate deformation result in higher compressive and tear strengths. Alginate impressions are more likely to tear during removal from the mouth when they are removed rapidly.

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 21

Impression materials can be classified as those that are flexible and those that are rigid at the time of removal from the mouth. A rigid impression material is restricted to applications in areas where undercuts exist.

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

What is an accepted method for modifying an impression tray?

A) Heating the tray to alter the configuration
B) Applying rope wax to the flanges
C) Adding compound to the edges
D) None of the above

Question 23

If an alginate impression is left to soak in a wet environment, the material will expand by which process?

A) Syneresis
B) Hysteresis
C) Imbibition
D) Dimensional change

Question 24

Which of the following are correct regarding silicone putties?

A) May be mixed with bare hands
B) Should not be mixed with bare hands
C) Should not be mixed when latex rubber gloves are worn
D) A and C
E) B and C

Question 25

The dimensional change of polyethers is higher than that of the addition silicones. The polyether absorbs water and changes dimensions if stored in contact with water until equilibrium is reached.

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 26

Early elastomeric impression materials include which of the following materials?

A) Polyether
B) Polyvinyl siloxane
C) Condensation silicone
D) All of the above
E) Only A and C

Question 27

Bubbles are produced in gypsum dies if poured within which time period?

A) Less than 1 hour
B) 1 hour
C) More than 1 hour
D) None of the above; bubbles are not an issue

Question 28

How should a maxillary impression tray fit?

A) Leave a 2-mm border around the alveolar process
B) Cover the distal of the most posterior tooth.
C) Include the maxillary tuberosity.
D) Extend past the mucobuccal fold.

Question 29

Which of the following is not true about alginate substitute materials?

A) Higher dimensional stability
B) Greater accuracy
C) Better recovery
D) Lower cost

Question 30

Which of the following factors limit the accuracy of wax bite registrations?

A) Distortion on removal
B) Release of internal stress on storage
C) Minimal dimensional changes from mouth to room temperature
D) A, B, and C
E) A and B

Question 31

What is/are the advantage(s) of using premeasured packets of alginate impression material?

A) Impervious to moisture
B) Less expensive than cans
C) Premeasured for a full arch
D) All of the above
E) Only A and C

Question 32

Why is it important to use vinyl gloves or bare hands to mix polyvinyl putty materials?

A) Many patients are allergic to latex.
B) Latex gloves retard the setting of the material.
C) Latex gloves accelerate the setting of the material.
D) A and C are correct.
E) A and B are correct.

Question 33

Of the following, which will alter setting times for alginates?

A) Decreased water temperature
B) Increased water temperature
C) Decreased powder
D) A, B, and C
E) Only A and B

Question 34

What is the dimensional change of addition silicone after 24 hours?

A) ( -0.1% )
B) ( -1% )
C) ( 0.1% )
D) ( 1% )

Question 35

Alginates, when properly mixed by hand, should develop a _________ consistency free of __________ in less than 1 minute for the normal set material and should be suitable for making impressions in the mouth.

A) thixotropic; bubbles
B) thixotropic; graininess
C) smooth and creamy; bubbles
D) smooth and creamy; graininess

Question 36

Digital impressions are not as accurate as elastomeric impressions. CAD/CAM requires a milling machine in order fabricate the indirect restoration.

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 37

Which of the following is correct regarding addition silicone?

A) Hydrophylic
B) Hydrophobic
C) High viscosity
D) Low dimensional change

Question 38

What is an advantage of using an elastomeric impression material over an irreversible hydrocolloid?

A) Less expensive
B) Reversible process
C) Greater dimensional accuracy
D) Best material for study models

Question 39

Alginate should be mixed by adding powder to water. Alginate should be mixed with a narrow, pliable spatula.

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 40

Which solutions are used to disinfect an impression?

A) Alcohol
B) Iodophor
C) Sodium hypochlorite
D) All of the above
E) Only B and C

Question 41

Compare and contrast alginate with elastomeric impression materials.

Question 42

Explain why an elastomeric bite registration might be preferable to a wax bite registration.