Impression Materials Flashcards
T/F: Good handling properties, transmission of information to models, and reproduction of detail are important characteristics of impression materials.
True
Impression materials are divided into what three physical conditions?
- rigid
- plastic
- ViscoElastic
ZOE and Plaster are _____ set materials.
Rigid
Wax and Compound are _____ set materials.
Plastic
Hydrocolloids and Elastomers are _____ set materials.
ViscoElastic
T/F: Agar is a reversible hydrocolloid.
True
T/F: Alginate is a reversible hydrocolloid.
False: alginate is irriversible
Polysulfide, Silicone, and Polyether are what type of impression material?
Synthetic Elastomers (ViscoElastic)
T/F: Alginate sets by crosslinking iron ions.
False: crosslinked by CALCIUM ions (calcium sulfate dihydrate)
T/F: Positive handling properties of alginate are established by diatomaceous earth.
True
Reproduction of detail is determined by _____ and ____ of the impression material.
viscosity
wettability
T/F: The contact angle is important for the oral environment and pouring up with gypsum.
True
True or False: Alginate has poor dimensional stability.
True
Alginate should be poured within _____ minutes.
ten
T/F: Agar has a lesser degree of recovery when compared to Alginate.
FALSE
T/F: Alginate is more accurate than Agar.
FALSE
The greater accuracy of agar is due to the greater degree of _______ around the undercuts of teeth.
recovery after deformation
Tear strength is a function of rate of _____.
strain
T/F: Polysulfide impression materials are considered to be the new elastic impression material.
True
______ is a low molecular weight oligomer that contains reactive mercaptan groups.
Polysulfide
T/F: Polysulfide conforms well to a prepared tooth, resulting in good surface detail.
True
Polysulfide oxidized by ______ = polysulfide rubber with ___ condensate.
lead dioxide (or copper hydroxide) water
T/F: For polysulfide to be accurate, the material requires a rigid custom tray for minimal thickness of impression material.
True
T/F: Polysulfides do not recover from permanent deformation as well as some other impression materials.
True
T/F: Models should be poured as quickly as possible for all impression materials.
False, not PVS
T/F: Polysulfide is the most expensive elastomer.
False (among the least expensive)
T/F: You can add additional layers to polysulfide.
True, it bonds to itself
T/F: Polysulfide shrinkage is reduced due to attachment of the material to the mouth.
False, due to attachment to the TRAY
T/F: Polysulfide can stain clothing.
True
T/F: Polysulfide is fast setting.
False
T/F: Polysulfide tastes good.
False
T/F: Polysulfide should be poured within 10 mins.
False, within 1 hour
Polysiloxanes (silicones) are inherently ______ but addition type can be made _____.
hydrophobic
hydrophilic
T/F: Polysiloxanes are made hydrophilic by the addition of surfactant.
True
T/F: Polysiloxanes taste better than polysulfides.
True
What is major consideration in transferring polysiloxane into models?
siloxanes can cause voids upon addition of stone slurry
T/F: Siloxanes are less stable than alginate or polysulfide.
False, more stable
T/F: When using condensation silicones, models may be poured any time within a few days.
False, pour as quickly as possible, after one hour the dimensional change increases at a constant rate
T/F: Condensations silicones taste bad and stain clothing.
FALSE, no staining and no objection to tastes
T/F: Condensation silicones have poor dimensional stability.
True
What are the major issues with condensation silicones? (2)
- stability after cure
2. mixing/handling properties (paste + liquid system)
Addition silicones are very ______ _____. Condensation silicones are dimensionally unstable.
(+) dimensionally stable
PVS is which type of imppresion material?
Addition silicone
T/F: PVS is a two part system.
True, the spiral tips mix it up and allow for hydrosilation reaction to produce chain lengthening and cross linking
Why should you wait before pouring PVS impressions?
the secondary reaction produces hydrogen, all hydrogen should be liberated before pouring the models… would cause bubbles!
T/F: The working time of PVS can be lengthened.
True, by addition of a retarder
T/F: Polyethers are hydrophilic.
True
T/F: Polysiloxanes are hydrophobic.
True
T/F: Polyethers taste bad.
True
When using polyether, contact of the unmixed ester with skin or mucosa could cause ____.
contact dermatitis
T/F: Polyether requires a custom tray.
True
Polyether is difficult to remove from _____.
undercuts
What are the four requirements of “ideal” impression materials?
- low cost
- long shelf life
- biocompatibility
- pleasant to patient
Which impression materials have good wetting on moist oral structures (low contact angle, easy to pour)?
agar
alginate
polysulfide
Which impression materials have fair/good wetting (aka ease of pouring)?
condensation silicone
addition silicone
polyether
Which material has the highest tear strength?
Polysulfide
Vinylsiloxane ether (VSE) is a new material that incorporates aspects of two materials to make a better impression. The _____ component acts as a surfactant.
polyether
(polyethers are hydrophilic)
“ethers like water”….to remember, think “i like Easter”
T/F: Both traditional and digital impression will produce clinically acceptable crowns.
True
T/F: There is a greater margin of error with digital impressions.
True
T/F: Prostheses fabricated from digital impressions showed fewer gaps in the occlusal surfaces.
False, MORE gaps
In the additive printing process, a slurry of zirconia and dispersants are ____ at 1450 Celsius.
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)
T/F: 3D printing can be used in dentistry for surgical guides, wax ups, models, and methacrylate based resins (provisionals).
True
