Impression Material Basics
The two major categories of impression materials that are based on their final physical properties.
What are elastic and nonelastic impression materials?
This popular impression material is classified as an irreversible hydrocolloid.
What is alginate?
This elastomeric material is also commonly called addition silicone or PVS.
What is vinyl polysiloxane (VPS/PVS)?
I’m an elastic impression material, but unlike alginate, I can be softened and hardened repeatedly because I undergo a reversible sol-gel transition. Who am I?
What is agar?
The faster you mix alginate, the faster it will set.
What is False?
Alginate's setting time is primarily affected by factors such as water temperature and the manufacturer's formulation—not simply how quickly you mix it.
The type of impression material that can be removed from undercuts because it has the ability to flex and recover.
What are elastic impression materials?
These are two common uses of alginate.
What are preliminary impressions and study/orthodontic models?
These are four non-aqueous elastomeric impression materials.
What are polysulfides, silicones, polyethers, and vinyl polysiloxanes?
I’m a rigid impression material that comes in colors such as red, gray, or green. Who am I?
What is impression compound?
An impression tray should extend far enough to capture the desired anatomy but should not impinge on the patient's tissues.
What is True?
The three materials that are classified as nonelastic impression materials.
What are impression plaster, impression compound, and zinc oxide-eugenol impression paste?
When mixing alginate, using this type of water will give you a longer working and setting time.
What is cold/colder water?
This elastomer releases ethyl alcohol as a byproduct during its setting reaction.
What is condensation silicone?
I’m a rigid impression material that is considered by many to be the best overall material for making impressions of completely edentulous patients—but I need to be poured soon after the impression is made. Who am I?
What is zinc oxide-eugenol impression paste?
The thicker the alginate impression material, the more accurate the impression will automatically be.
What is False?
Accuracy depends on proper material manipulation, tray selection, bulk, support, and other factors—not simply making the material thicker.
These impression materials are generally used for edentulous patients with minimal undercuts because they are rigid.
What are nonelastic impression materials?
This is the term for water entering an alginate impression, while this is the term for water leaving it.
What are imbibition and syneresis (respectively)?
This elastomer is known for excellent wettability and good dimensional stability but relatively poor tear strength.
What is polyether?
I’m an impression material that is supplied as two pastes mixed in a 1:1 ratio. I have a long working and setting time, good tear strength, and flexibility—but my odor is definitely not winning any awards. Who am I?
What is polysulfide?
If an alginate impression looks perfect immediately after removal, it can safely be wrapped in a paper towel and stored overnight before pouring.
What is False?
Alginate is dimensionally unstable and should generally be poured promptly according to the manufacturer's instructions.
A patient has significant undercuts, and the dentist chooses a rigid impression material. This is the main reason that choice could cause a problem during removal.
What is the lack of flexibility/spring-like quality of nonelastic materials, making them difficult to remove from undercuts?
("The lack of flexibility or spring-like quality" is also acceptable)
An alginate impression is left sitting out for several hours before the cast is poured. This is the main problem you would expect.
What is dimensional distortion caused by water loss or gain?
Of condensation silicone and addition silicone, this material has better dimensional stability because it does not release a volatile alcohol byproduct during setting.
What is addition silicone (PVS)?
I’m an addition silicone impression material. If you use latex gloves while handling me, the sulfur can poison my platinum catalyst and cause me to set improperly—or not set at all—in the contaminated area. Who am I?
What is vinyl polysiloxane (addition silicone/PVS)?
Two elastomeric impression materials can have different properties even though they are both classified as elastic impression materials.
What is True?