Deck 15: Impression Materials

Question 1

When using elastomers,which of the following should be blocked out with utility wax to prevent the impression material from locking under them and preventing removal of the impression tray?
1)Undercuts around bridge pontics
2)Open embrasures around periodontally involved teeth
3)Fixed implant fixtures
4)Hamular notch

A) 1,2,3,4
B) 1,2,3
C) 2,3,4
D) 1,3,4

Answer 1

1,2,3

Question 2

For a maxillary alginate impression,the operator stands just _____ the patient at the _____ o'clock position and retracts the corner of the mouth with the side of the tray while retracting the other corner of the mouth with the index finger of the other hand.

A) in front of;5
B) in front of;7
C) behind;1
D) behind;11

Answer 2

behind;11

Question 3

Which of the following disinfectants are compatible with addition silicone impression materials?
1)1:10 sodium hypochlorite
2)1:213 iodophors
3)Glutaraldehydes
4)Complex phenolics

A) 1,2,3,4
B) 1,2,3
C) 2,3,4
D) 2,3

Answer 3

1,2,3,4

Question 4

The temperature at which the hydrocolloid liquefies is not the same temperature at which it solidifies.What is this property called?

A) Hysteresis
B) Hydrophilic
C) Hydrophobic
D) Agglutination

Question 5

Mixed alginate should be loaded into the impression tray in _____ increments as _____ as possible.

A) large;quickly
B) large;slowly
C) small;quickly
D) small;slowly

Question 6

Containers of alginate such as cans or plastic containers should be turned end-over-end a few times to decompress the powder and mix the ingredients.Alginate dust is potentially hazardous to inhale because it contains silicon dioxide in the diatomaceous earth fillers.

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 7

_____ gloves should be used when mixing PVS putty.

A) Utility
B) Nitrile
C) Latex
D) Vinyl

Question 8

What is occurring when an alginate impression appears to sweat,showing droplets on the surface?

A) Syneresis
B) Hysteresis
C) Imbibition
D) Dehydration

Question 9

The completed impression forms a _____ reproduction of the teeth and tissues,and the replica or model forms a _____ replica of the teeth and tissues.

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

Question 10

Which of the following is an elastic impression material?

A) Impression wax
B) Impression plaster
C) Vinyl polyether silicone
D) Dental impression compound

Question 11

Some practitioners use a specially formulated addition silicone material in an automatic mixing cartridge system to make which types of dies?

A) Direct composite inlays
B) Indirect composite inlays
C) Porcelain jacket crowns
D) Porcelain-fused-to-metal crowns

Question 12

Which statement is correct regarding alginate hydrocolloid?

A) Fast-set alginate has a working time of 2 to 3 minutes.
B) Some moisture will be lost from the impression even in 100% humidity.
C) Alginate hydrocolloid should be removed slowly to prevent deformation of critical surfaces.
D) Adjusting the powder-to-water ratio is the best way to lengthen or shorten the setting time.

Question 13

Which of the following is the most widely used dental impression material?

A) Reversible hydrocolloid
B) Irreversible hydrocolloid
C) Addition of silicone impression material
D) Condensation silicone impression material

Question 14

Which of the following elastomers are the most hydrophilic?

A) Polyethers
B) Polysulfides
C) Addition silicones
D) Condensation silicones

Question 15

Which of the following impression materials has the smallest dimensional change on setting of all elastomeric and hydrocolloid impression materials?

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

Question 16

Which statement is true about impression trays?

A) The triple tray is a custom full-arch tray used for bite registration.
B) Stock trays are made of plastic rather than metal and can be solid or perforated.
C) Plastic trays are inexpensive and disposable,whereas metal trays are more expensive and must be cleaned and sterilized between uses.
D) Custom trays are constructed in the patient's mouth with chemically cured,light-cured,or thermoplastic resins on casts of the teeth.

Question 17

What is the ideal time frame for pouring an alginate impression?

A) An hour
B) A day
C) A week
D) A month

Question 18

Which of the following is true for hydrocolloids in dentistry?

A) Agar hydrocolloid is a reversible hydrocolloid.
B) Agar hydrocolloid requires the use of custom impression trays.
C) The main clinical use of reversible hydrocolloid is for impressions for diagnostic casts.
D) When agar powder is mixed with water,it forms a gluelike suspension that entraps the water,making a colloidal suspension called a gel.

Question 19

Which of the following is true of vinyl polyether silicone?

A) It is hydrophobic.
B) It flows well but has low tear strength.
C) It can tolerate a little moisture around the preparation.
D) It is available in three viscosities: light,monophase,and heavy.

Question 20

A properly extended maxillary alginate impression tray will extend posteriorly enough to include which oral landmark?

A) Retromolar pad
B) Hamular notch
C) Soft palate
D) Uvula

Question 21

Match the items with the correct description below.
Colloid

A)An alginate impression material that is mixed to a sol state and as it sets converts to a gel by a chemical reaction that irreversibly changes its nature
B)Gluelike material composed of two or more substances in which one substance does not go into solution but is suspended within another substance
C)An agar impression material that can be heated to change from a gel into a fluid state that can flow around the teeth
D)A water-based colloid used as an elastic impression material
E)A versatile irreversible hydrocolloid that is the most used impression material in the dental office

Question 22

When mixing alginate,as the water temperature increases,the working time:

A) increases.
B) decreases.
C) stays the same.

Question 23

A dental impression is a/an _____ reproduction of the teeth.

A) positive
B) negative
C) distorted
D) approximate

Question 24

Match the items with the correct description below.
Alginate

A)An alginate impression material that is mixed to a sol state and as it sets converts to a gel by a chemical reaction that irreversibly changes its nature
B)Gluelike material composed of two or more substances in which one substance does not go into solution but is suspended within another substance
C)An agar impression material that can be heated to change from a gel into a fluid state that can flow around the teeth
D)A water-based colloid used as an elastic impression material
E)A versatile irreversible hydrocolloid that is the most used impression material in the dental office

Question 25

When should impressions be disinfected?

A) At the dental lab check-in
B) Before rinsing with water
C) At the chairside upon removal
D) For an hour before pouring in gypsum

Question 26

Which characteristic should be considered when choosing an impression tray?

A) Be large enough to fit all oral structures
B) Be rigid to support the impression material
C) Accurately reproduce vestibules
D) All of the above are considered.

Question 27

Match the items with the correct description below.
Hydrocolloid

A)An alginate impression material that is mixed to a sol state and as it sets converts to a gel by a chemical reaction that irreversibly changes its nature
B)Gluelike material composed of two or more substances in which one substance does not go into solution but is suspended within another substance
C)An agar impression material that can be heated to change from a gel into a fluid state that can flow around the teeth
D)A water-based colloid used as an elastic impression material
E)A versatile irreversible hydrocolloid that is the most used impression material in the dental office

Question 28

Impressions taken with polyvinyl siloxane should be poured within:

A) 30 minutes.
B) 1 hour.
C) 1 day.
D) 1 week.

Question 29

Why would a dentist choose to use an addition silicone over a condensation silicone?

A) Addition is stronger than condensation.
B) Addition does not distort as badly.
C) Addition is cleaner to use.
D) Addition tastes better.

Question 30

What could occur if a cast is made from an improperly disinfected impression?

A) Will not harbor microorganisms
B) Should be immersed in solution
C) Should be stored for 24 hours first
D) Cannot be disinfected,so start over

Question 31

When preparing to take an alginate impression,which of the following is not necessary?

A) Fluff the material to mix.
B) Wear a mask and eyewear.
C) Have patient use antibacterial rinse.
D) Use a try-in tray for fit.

Question 32

Match the items with the correct description below.
Reversible hydrocolloid

A)An alginate impression material that is mixed to a sol state and as it sets converts to a gel by a chemical reaction that irreversibly changes its nature
B)Gluelike material composed of two or more substances in which one substance does not go into solution but is suspended within another substance
C)An agar impression material that can be heated to change from a gel into a fluid state that can flow around the teeth
D)A water-based colloid used as an elastic impression material
E)A versatile irreversible hydrocolloid that is the most used impression material in the dental office

Question 33

List and describe the different types of impression materials suitable for crown and bridge procedures.

Question 34

Impressions taken with polyether should be poured within what time period?

A) 30 minutes
B) 1 hour
C) 1 day
D) 1 week

Question 35

Of the items listed,which would not be made from an alginate impression?

A) Mouth guard
B) Bleaching tray
C) Retainer
D) Onlay

Question 36

Match the items with the correct description below.
Irreversible hydrocolloid

A)An alginate impression material that is mixed to a sol state and as it sets converts to a gel by a chemical reaction that irreversibly changes its nature
B)Gluelike material composed of two or more substances in which one substance does not go into solution but is suspended within another substance
C)An agar impression material that can be heated to change from a gel into a fluid state that can flow around the teeth
D)A water-based colloid used as an elastic impression material
E)A versatile irreversible hydrocolloid that is the most used impression material in the dental office