Deck 22: Impression Materials and Laboratory Procedures

Question 1

An impression is a negative reproduction. A cast is a positive reproduction.

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

Answer 1

Both statements are true.

Question 2

The anterior portion of a trimmed maxillary model will be:

A) pointed
B) rounded
C) squared
D) beveled

Answer 2

pointed

Question 3

A preliminary impression is used to fabricate:

A) custom trays
B) indirect restorations
C) partial or full dentures
D) implants

Answer 3

custom trays

Question 4

Which correctly describes the pouring method of a dental cast?

A) The art portion of a cast is poured first in the double-pour method.
B) The completed box should extend at least 1 inch above the palatal area of the maxillary impression when the box-and-pour method is used.
C) The inverted-pour method consists of mixing one large amount of plaster or stone and pouring both portions of the model in a single step.
D) The "box" used in the box-and-pour method is made of baseplate wax.

Question 5

Which is NOT used for pouring diagnostic casts?

A) Model plaster
B) Dental stone
C) Acrylic resin
D) High-strength stone

Question 6

Light-body elastomeric material is placed in the sulcus, around and over the prepared tooth, and onto the surrounding tissue with a:

A) syringe
B) carrier
C) spatula
D) brush

Question 7

When loading a tray for an upper impression, place:

A) more material toward the anterior and labial edges
B) more material in the palatal area
C) the material evenly in the tray
D) more material toward the posterior and palatal areas

Question 8

Which forms the art portion of the cast?

A) Teeth
B) Oral mucosa
C) Muscle attachments
D) Base

Question 9

When taking a wax bite registration, the patient is directed to:

A) bite with the posterior teeth first
B) close normally and gently
C) occlude with lateral movements
D) bite with the anterior teeth first

Question 10

The three classifications of impressions in dentistry are:

A) prospective, retrospective, and introspective registrations
B) preliminary, functional, and occlusal, or bite, registrations
C) preliminary, final, and occlusal, or bite, registrations
D) diagnostic, functional, and determinative registrations

Question 11

A water temperature of 80° F (26.6° C) produces which effect on a gypsum mix?

A) The mix will set rapidly.
B) The mix will set with a grainy texture.
C) The mix will set slowly.
D) The mix will not set.

Question 12

Which impression tray covers half of a dental arch?

A) Full
B) Section
C) Quadrant
D) Custom

Question 13

The irreversible hydrocolloid material used most extensively for preliminary impressions is:

A) light-bodied material
B) alginate
C) polysulfide
D) polyether

Question 14

Which statement is true?

A) Model plaster is stronger than dental stone.
B) Dental stone is used when dimensional accuracy is not critical.
C) High-strength stone is a form of gypsum.
D) All gypsum products have the same powder-to-water ratio.

Question 15

The dental assistant should be familiar with all types of impression trays, because the type of tray selected for a procedure depends on the assistant's preference.

A) Both the statement and the reason are correct and related.
B) Both the statement and the reason are correct but not related.
C) The statement is correct, but the reason is not.
D) The statement is not correct, but the reason is correct.

Question 16

A custom impression tray is made from:

A) resin
B) plastic
C) metal
D) gauze

Question 17

Bite registration paste is applied with which tray?

A) Perforated
B) Gauze
C) Plastic sooth
D) Water coolant

Question 18

An extruder gun is used for which impression mix?

A) Automix system
B) Paste system
C) Putty impression material
D) Tabletop mixing unit

Question 19

Alginate impressions are disinfected by:

A) soaking in glutaraldehyde
B) submersion in disinfecting solution overnight
C) wetting with isopropyl alcohol
D) spraying the alginate with a disinfectant

Question 20

Alginate impressions are removed from the mouth by:

A) using a gentle rocking movement
B) using one quick, snap-out motion
C) twisting the tray sideways
D) using a vigorous back-and-forth action

Question 21

A preliminary impression may be separated from its dental model within 15 minutes of being poured.

Question 22

Which slows the set of a gypsum cast?

A) Using model plaster instead of dental stone
B) Adding a little extra powder to the mix
C) Using warm water in the mix
D) Mixing gently for a short period of time

Question 23

Dentists prefer to use plaster for diagnostic casts, due to its strength and long shelf life.

Question 24

Alginate should be mixed:

A) without touching the sides of the bowl
B) firmly against the sides of the bowl
C) for 3 minutes
D) for 5 minutes

Question 25

Which step prepares a dental model for trimming?

A) Mix a slurry of gypsum and water and fill in any voids.
B) Draw a line inch behind the maxillary tuberosities.
C) Soak the art portion of the model in a bowl of water for at least 5 minutes.
D) Remove gypsum beads from the model with a laboratory knife.

Question 26

Which material is elastic and reversible?

A) Zinc oxide eugenol impression paste
B) Agar
C) Alginate
D) Impression compounds

Question 27

Although the technique may vary, when one is assisting a dentist in taking an elastomeric impression, mix the light-bodied material first.

Question 28

After taking an alginate impression, the cast should be fabricated within:

A) 15 minutes
B) 30 minutes
C) 1 hour
D) 24 hours

Question 29

Which tray produces a final impression and bite registration at the same time?

A) Perforated
B) Triple
C) Plastic sooth
D) Water coolant

Question 30

To remove air bubbles from automix final impression material:

A) allow the powder to settle into the water for about 30 seconds
B) extrude a small amount of unmixed material onto a gauze pad
C) place the mix on a vibrator platform until air bubbles rise to the surface
D) press the material down to the base of the tray and smooth the surface with a wet finger

Question 31

Which final impression material has the longest setting time?

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

Question 32

Fast-set alginate has a working time of minutes.

Question 33

The art portion of the cast should be no more than one-half inch thick and should make up one-third of the overall cast.

Question 34

After seating and preparing the patient for preliminary impressions, the next step is to mix the alginate.

Question 35

Gypsum should be mixed:

A) vigorously against the sides of the bowl
B) in steady increments with a slow stirring motion
C) for 2 minutes
D) for 3 minutes

Question 36

The bite registration establishes the proper centric relationship when fabricating a permanent crown.

Question 37

Heavy-body material is the thickest of the three elastomeric impression materials.