Deck 8: Impression Materials

Question 1

The main disadvantage of alginate hydrocolloid impression material in contrast to an elastomeric impression is:

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

Answer 1

it does not transfer as much surface detail to gypsum dies.

Question 2

Recommendations for mixing the alginate include:

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.

Answer 2

adding the powder to the water.

Question 3

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

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

Answer 3

in air approaching 100% relative humidity

Question 4

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

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

Question 5

Permanent deformation increases when:

A) the time before testing is lengthened.
B) the amount of deformation during removal is decreased.
C) the time that is held under compression is decreased.
D) thinner mixes are used.

Question 6

With time,alginate gels shrink and lose water through a process called:

A) imbibition.
B) syneresis.
C) agglomeration.
D) agglutination.
E) dehydration.

Question 7

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) 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 8

Alginate hydrocolloid is supplied:

A) in compules.
B) in two syringes to be mixed together.
C) in two tubs as a putty system for hand kneading.
D) as a thixotropic gel.
E) as a powder.

Question 9

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

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

Question 10

Alginate impression material may be referred to as a(n):

A) addition silicone.
B) condensation silicone.
C) polyether.
D) irreversible hydrocolloid.
E) reversible hydrocolloid.

Question 11

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 12

The best method for delaying the setting of alginate is to:

A) reduce the water temperature.
B) increase the water temperature.
C) use a thinner mix of alginate.
D) use a thicker mix of alginate.

Question 13

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

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

Question 14

The mixing time of fast-setting alginate is:

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

Question 15

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

Question 16

Which of the following is a rigid dental impression material?

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

Question 17

Alginate hydrocolloid is recommended:

A) for preparation of study models.
B) for impressions of cavity preparations.
C) in the preparation of athletic mouth protectors.
D) for A, B, and C.
E) for A and C.

Question 18

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 19

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 20

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

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

Question 21

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 22

A maxillary impression tray should:

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 23

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 24

Advantages of elastomeric impression materials in contrast to alginate hydrocolloid materials include:

A) greater accuracy.
B) dimensional stability with time.
C) ability to record detail.
D) both A and C.

Question 25

An advantage of using an elastomeric impression material over an irreversible hydrocolloid is it:

A) is less expensive.
B) is the best material for study models.
C) has greater dimensional accuracy.
D) is a reversible process.

Question 26

Which of the following factors limit(s)the accuracy of wax bite registrations?

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

Question 27

An accepted method for modifying an impression tray would include:

A) applying rope wax to the flanges.
B) heating the tray to alter the configuration.
C) adding compound to the edges.
D) none of the above.

Question 28

Early elastomeric impression materials included:

A) polyether.
B) condensation silicone.
C) polysulfide.
D) all of the above.
E) only A and C.

Question 29

An advantage of using premeasured packets of alginate material includes packets are:

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 30

Solutions used to disinfect an impression would include:

A) alcohol.
B) sodium hypochlorite.
C) iodophor.
D) all of the above.
E) only B and C.

Question 31

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 32

Dimensional change of addition silicone after 24 hours is:

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

Question 33

If an alginate impression is left to sit in a dry environment,the material will shrink.This process is known as:

A) imbibition.
B) syneresis.
C) dimensional change.
D) hysteresis.

Question 34

The strength of alginate material _____ if a _____ mixture is used.

A) increases; thinner.
B) increases; thicker.
C) decreases; thinner.
D) decreases; thicker.
E) Both B and D are correct.
F) Both A and C are correct.

Question 35

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 36

Addition silicone putties:

A) should not be mixed with bare hands.
B) may 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 37

Bubbles are produced in gypsum dies if poured in:

A) less than 1 hour.
B) 1 hour.
C) more than 1 hour.
D) none of the above; bubbles are not an issue.

Question 38

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

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