Chapter 15 Impression Material Flashcards
Positive replicas of the teeth and surrounding oral tissues and structures produced from impressions that create a negative representation of the teeth, commonly called study models
Diagnostic casts
An impression of the dentition and surrounding tissue taken as a precursor to other treatment, often used to make casts of oral structures for planning, and to create custom trays or provisional restorations
Preliminary impression
A detailed impression of oral structures used to make an accurate cast from which restorations or prosthesis are made
Final impression
An impression of the upper and lower teeth in the patient’s normal bite relation
Bite registration
Ability of a material to maintain its size and shape over a period of time
Dimensional stability
Ability of a material to adapt to and flow over the surfaces of the oral structures to record fine detail
Accuracy
Ability to avoid tearing when the material is in thin sections
Tear resistance
Glue-like material composed of two or more substances in which one substance does not go into solution but is suspended within another substance; it has atleast two phases: a liquid phase called a sol and a semisolid phase called a gel
Colloid
A water-based colloid used as an elastic impression material
Hydrocolloid
An agar impression material that can be heated to change a gel into a fluid sol state that can flow around the teeth, and then cooled to gel again to make an impression of the shapes of the oral structures
Reversible Hydrocolloid
An alginate impression material that is mixed to a sol state and as it sets converts to a gel by a chemical reaction that irreversibly changes its nature
Irreversible Hydrocolloid
A powder derived from seaweed that is a major component of reversible hydrocolloid
Agar
Liquid state in which colloid particles are suspended by cooling or a chemical reaction, it can change into a gel
Sol
A semisolid state in which colloid particles form a framework that traps liquid
Gel
A versatile irreversible hydrocolloid that is the most used impression material in the dental office, it lacks the accuracy and fine surface detail needed for impressions for crown and bridge procedures
Alginate
A characteristic of gels when left standing to contract and squeeze out some liquid that then accumulates on the surface
Syneresis
Highly accurate elastic impression materials that have qualities similar to rubber, they are used extensively in indirect restorative techniques, such as crown and bridge procedures
Elastomers
The act of absorbing moisture
Imbibition
A chemical that lowers the surface tension of a substance so that it is more readily wetted, for ex. oil beads on the surface of water, but soap acts as a surfactant to allow the oil to spread over the surface
Surfactant
An elastic impression material that has sulfur containing functional groups, it also has been referred to as rubber base impression material
Polysulfide
A silicone rubber impression material that sets by linking molecules in long chains but produces a liquid by-product by condensation
condensation silicone
A silicone rubber impression material that sets by linking molecules in long chains but produces no by-product, the most commonly used addition silicones are the polyvinyl siloxanes
Addition silicone
Very accurate addition silicone elastomer impression material, it is used extensively for crown and bridge procedures because of its accuracy, dimensional stability and ease of use
Polyvinyl Siloxane PVS
A rubber impression material with ether functional groups, it has high accuracy and is popular for crown and bridge procedures
Polyether
