Dental materials - Impression materials Flashcards
What kind of reproduction is an impression?
Impression = negative replica
What kind of reproduction is used in casting an impression?
Cast of impression = positive replica
How are impression materials classified?
Via
Clinical - mucostatic or mucocompressive
Properties - Elastic or non-elastic
What CLINICAL classification of impression material is a low viscosity alginate?
Mucostatic
Describe the type of impression that would be given using a low viscosity alginate (mucostatic) impression material.
Produces an impression of the undisplayed soft tissues
What CLINICAL classification of impression material is a high viscosity alginate?
Mucocompressive
Describe the type of impression that would be given using a high viscosity alginate (mucocompressive) impression material.
Produces a denture with displayed soft tissues
Produces a denture which is more stable during function than at rest
What is the advantage of using an elastic impression material?
They can undergo strain during removal yet return to the impression shape after removal.
(able to overcome the bulbous part of the tooth and not completely deform)
In terms of removal of the elastic impression material, how do you prevent deformation?
Reduce load time by removing with a sharp pull.
List the types of elastic impression materials.
Hydrocolloids such as;
Agar
Alginate
Elastomers such as;
Polyethers
Silicones
Polysulphides
What are 3 properties you have to consider with an impression material?
Accuracy
Patient comfort
Operator control
What are the IDEAL properties to ensure that there is accuracy of the impression material?
High flow - to capsure surface detail.
High elasticity - recovery once removed.
Low thermal contraction - Ensures impression doesn’t contract when moving from the oral cavity to the external environment (change in temperatures)
High tear strength - doesn’t tear when removed
Storage - doesn’t deform over time with changes to moisture.
What are the IDEAL properties to ensure that the impression material is comfortable for the patient?
Fast setting
Non-irritant/toxic
Acceptable taste and smell
Doesn’t damage the oral tissues
What are the IDEAL properties to ensure that the impression material is comfortable for the operator?
Reasonable quick setting
Simple technique
Can be decontaminated
What impression material is an irreversible hydrocolloid?
Alginate
