Impression Materials

Question 1

T/F: Good handling properties, transmission of information to models, and reproduction of detail are important characteristics of impression materials.

Answer 1

True

Question 2

Impression materials are divided into what three physical conditions?

Answer 2

1. rigid
2. plastic
3. ViscoElastic

Question 3

ZOE and Plaster are _____ set materials.

Answer 3

Rigid

Question 4

Wax and Compound are _____ set materials.

Answer 4

Plastic

Question 5

Hydrocolloids and Elastomers are _____ set materials.

Answer 5

ViscoElastic

Question 6

T/F: Agar is a reversible hydrocolloid.

Answer 6

True

Question 7

T/F: Alginate is a reversible hydrocolloid.

Answer 7

False: alginate is irriversible

Question 8

Polysulfide, Silicone, and Polyether are what type of impression material?

Answer 8

Synthetic Elastomers (ViscoElastic)

Question 9

T/F: Alginate sets by crosslinking iron ions.

Answer 9

False: crosslinked by CALCIUM ions (calcium sulfate dihydrate)

Question 10

T/F: Positive handling properties of alginate are established by diatomaceous earth.

Answer 10

True

Question 11

Reproduction of detail is determined by _____ and ____ of the impression material.

Answer 11

viscosity

wettability

Question 12

T/F: The contact angle is important for the oral environment and pouring up with gypsum.

Answer 12

True

Question 13

True or False: Alginate has poor dimensional stability.

Answer 13

True

Question 14

Alginate should be poured within _____ minutes.

Answer 14

ten

Question 15

T/F: Agar has a lesser degree of recovery when compared to Alginate.

Answer 15

FALSE

Question 16

T/F: Alginate is more accurate than Agar.

Answer 16

FALSE

Question 17

The greater accuracy of agar is due to the greater degree of _______ around the undercuts of teeth.

Answer 17

recovery after deformation

Question 18

Tear strength is a function of rate of _____.

Answer 18

strain

Question 19

T/F: Polysulfide impression materials are considered to be the new elastic impression material.

Answer 19

True

Question 20

______ is a low molecular weight oligomer that contains reactive mercaptan groups.

Answer 20

Polysulfide

Question 21

T/F: Polysulfide conforms well to a prepared tooth, resulting in good surface detail.

Answer 21

True

Question 22

Polysulfide oxidized by ______ = polysulfide rubber with ___ condensate.

Answer 22

lead dioxide (or copper hydroxide)
water

Question 23

T/F: For polysulfide to be accurate, the material requires a rigid custom tray for minimal thickness of impression material.

Answer 23

True

Question 24

T/F: Polysulfides do not recover from permanent deformation as well as some other impression materials.

Answer 24

True

Question 25

T/F: Models should be poured as quickly as possible for all impression materials.

Answer 25

False, not PVS

Question 26

T/F: Polysulfide is the most expensive elastomer.

Answer 26

False (among the least expensive)

Question 27

T/F: You can add additional layers to polysulfide.

Answer 27

True, it bonds to itself

Question 28

T/F: Polysulfide shrinkage is reduced due to attachment of the material to the mouth.

Answer 28

False, due to attachment to the TRAY

Question 29

T/F: Polysulfide can stain clothing.

Answer 29

True

Question 30

T/F: Polysulfide is fast setting.

Answer 30

False

Question 31

T/F: Polysulfide tastes good.

Answer 31

False

Question 32

T/F: Polysulfide should be poured within 10 mins.

Answer 32

False, within 1 hour

Question 33

Polysiloxanes (silicones) are inherently ______ but addition type can be made _____.

Answer 33

hydrophobic | hydrophilic

Question 34

T/F: Polysiloxanes are made hydrophilic by the addition of surfactant.

Answer 34

True

Question 35

T/F: Polysiloxanes taste better than polysulfides.

Answer 35

True

Question 36

What is major consideration in transferring polysiloxane into models?

Answer 36

siloxanes can cause voids upon addition of stone slurry

Question 37

T/F: Siloxanes are less stable than alginate or polysulfide.

Answer 37

False, more stable

Question 38

T/F: When using condensation silicones, models may be poured any time within a few days.

Answer 38

False, pour as quickly as possible, after one hour the dimensional change increases at a constant rate

Question 39

T/F: Condensations silicones taste bad and stain clothing.

Answer 39

FALSE, no staining and no objection to tastes

Question 40

T/F: Condensation silicones have poor dimensional stability.

Answer 40

True

Question 41

What are the major issues with condensation silicones? (2)

Answer 41

1. stability after cure | 2. mixing/handling properties (paste + liquid system)

Question 42

Addition silicones are very ______ _____. Condensation silicones are dimensionally unstable.

Answer 42

(+) dimensionally stable

Question 43

PVS is which type of imppresion material?

Answer 43

Addition silicone

Question 44

T/F: PVS is a two part system.

Answer 44

True, the spiral tips mix it up and allow for hydrosilation reaction to produce chain lengthening and cross linking

Question 45

Why should you wait before pouring PVS impressions?

Answer 45

the secondary reaction produces hydrogen, all hydrogen should be liberated before pouring the models... would cause bubbles!

Question 46

T/F: The working time of PVS can be lengthened.

Answer 46

True, by addition of a retarder

Question 47

T/F: Polyethers are hydrophilic.

Answer 47

True

Question 48

T/F: Polysiloxanes are hydrophobic.

Answer 48

True

Question 49

T/F: Polyethers taste bad.

Answer 49

True

Question 50

When using polyether, contact of the unmixed ester with skin or mucosa could cause ____.

Answer 50

contact dermatitis

Question 51

T/F: Polyether requires a custom tray.

Answer 51

True

Question 52

Polyether is difficult to remove from _____.

Answer 52

undercuts

Question 53

What are the four requirements of "ideal" impression materials?

Answer 53

1. low cost 2. long shelf life 3. biocompatibility 4. pleasant to patient

Question 54

Which impression materials have good wetting on moist oral structures (low contact angle, easy to pour)?

Answer 54

agar alginate polysulfide

Question 55

Which impression materials have fair/good wetting (aka ease of pouring)?

Answer 55

condensation silicone addition silicone polyether

Question 56

Which material has the highest tear strength?

Answer 56

Polysulfide

Question 57

Vinylsiloxane ether (VSE) is a new material that incorporates aspects of two materials to make a better impression. The _____ component acts as a surfactant.

Answer 57

polyether (polyethers are hydrophilic) "ethers like water"....to remember, think "i like Easter"

Question 58

T/F: Both traditional and digital impression will produce clinically acceptable crowns.

Answer 58

True

Question 59

T/F: There is a greater margin of error with digital impressions.

Answer 59

True

Question 60

T/F: Prostheses fabricated from digital impressions showed fewer gaps in the occlusal surfaces.

Answer 60

False, MORE gaps

Question 61

In the additive printing process, a slurry of zirconia and dispersants are ____ at 1450 Celsius.

Answer 61

sintered - the slurry is extruded and gelled (aka: make a powdered material coalesce into a solid or porous mass by heating it, and usually also compressing it, without liquefaction)

Question 62

T/F: 3D printing can be used in dentistry for surgical guides, wax ups, models, and methacrylate based resins (provisionals).

Answer 62

True