Impression Materials Flashcards
What is non-elastic impression material good for
Non retentive areas (NOT INCISORS)
Soft tissue displacement (eg for dentures)
What are some examples of non elastic impression materials
Impression plaster (plaster of paris)
Impression compound
Zinc oxide eugenol
Impression waxes
What is impression plaster used for
Edentulous areas with minimal undercuts
Register jaw relations
Advantages of using impression plaster to take impression
Dimensionally stable (Retain original dimensions when subjected to changes in temperature and humidity)
Good surface detail
Minimal distortion of soft tissues
Is impression plaster strong
Low strength and brittle
What is impression compound used for
Edentulous area, make custom tray, impression of single tooth prep
Is impression compound thermoplastic or thermosetting
Thermoplastic, can be reheated and readapted
Disadvantages of using impression compound
Low thermal conductivity, take long time to cool down
Poor dimensional stability
Poor surface detail
Does impression compound have high CLT
Yes
Does impression compound cause distortion of soft tissues
No. Minimal flow on hardening to prevent distortion
What happens if you remove the material before material properly hardens
Residual stress, change shape
Type 1 vs type 2 impression compound
Type 1 impression compound is used for impressions, type 2 is used for trays
Type 2 impression compound flows less than type 1
What can cause distortion in non elastic impression materials
Improper softening (must use dry heat or water bath)
Removal before completely chilled
Not making cast after impression made
What are elastic impression materials good for
Can record undercuts in dentate, partially dentate, and edentulous patients
What are the two main classes of materials in elastic impression materials
Hydrocolloids and synthetic elastomers
