Flashcards in Impression Materials Deck (37)
What do dimensional changes need to add up to?
What are the three types of impression materials?
rigid, plastic and (visco)elastic
Viscoelastic impression materials are found as reversible (agar) or irreversible (alginate) ___.
Viscoelastic impression materials can also be found as synthetic ___. These are ___ that polymerize into ___.
elastomers; oligomers; elastomers
What are the different forms of synthetic elastomers?
polysulfide, silicone, polyether, and new product
Which is the most common for of synthetic elastomer?q
T/F. Light and heavy body impression materials are used separately to enhance the accuracy of the final impression.
False, they are used together.
T/F. The light impression material is used for detail while the heavy is used in the other areas.
Water is bound within a colloid matrix
Both Alginate (___)(reversible/irreversible) and Agar (___) (reversible/irreversible) lack dimensional stability with time and require ___ pouring of models.
irreversible; reversible; immediate
What type of polymer has no cross-linking and its physical state is reversibly controlled by temperature? For example, when heated it is fluid and when cooled it can be removed from the patient.
A ___ polymer is transformed from monomer to polymer and involves irreversible ___.
T/F. Condensation polymerization releases no by products.
False, addition polymerization releases no by-products whereas, condensation does.
During the change from liquid or paste into a solid, advantageous final properties are ___ (increased/decreased).
During the change from liquid/paste into a solid, the inherent density increase causes a volumetric ___ (shrinkage).
During the change from liquid/paste into a solid, heat of reaction causes material to ___ ___, but this is usually minor.
During the change from liquid/paste into a solid, there is a ___ on cooling.
Polysulfide low molecular weight oligomers containing reactive ___ groups.
Polysulfide oxidized by lead dioxide or copper hydroxide to form a polysulfide ___ with a ___ condensate. This stains and does not taste good.
T/F. For polysulfides to be accurate, this material requires a rigid custom tray for minimal thickness of impression materials.
T/F. Polysulfides recover from permenant deformation.
False, they do not recover from permanent deformation.
T/F. Polysulfides should be poured as quickly as possible.
Silicones (Polysiloxanes) are inherently ___ but the addition type can be made more ___.
What was the first type of silicone introduced?
How do you make the addition type of silicone more hydrophilic?
simple addition of surfactant or chemical incorporation of hydrophilic moieties into the silicone backbone.
Fluid material needs a ___ contact angle, therefore you want it to be ___.
Why are contact angles important?
unset impression material over wet oral structures
unset gypsum-water mix into set impression
Condensation silicone have low molecular weight oligomers containing reactive terminal ___ groups which react with ortho-ethyl silicate and stannous octoate to form the three dimensional network rubber with the liberation of ___ ___.
hydroxyl; ethyl alcohol
With addition silicone, in the presence of ___ acid, ionic polymerization produces chain-lengthening and cross linking.