Flashcards in Hydrocolloid impression material Deck (23):
What does high viscosity material give?
can displace soft tissues
What doe low viscosity material give?
more fine detail
tray may not contain
What do moist surfaces do to hydrocolloid imp materials?
does not give good detail
How are impression materials classified?
What are non elastic imp materials?
zinc oxide and euganol paste
What are elastic impression materials?
What is a reversible hydrocolloid?
What is an irreversible hydrocolloid?
How do hydrocolloids exist?
both reversible and irreversible exist in sol and gel form
What is a sol-gel reaction?
What is a gel to sol reaction?
increase in temperature
alginate can go in what direction?
sol to gel only
agar can go in what direction?
sol to gel and gel to sol
What are synthetic elastomers?
What is agar used for?
What does agar require?
water bath conditioning:
100 degrees- gel to sol
65 degrees- holding temperature
45 degrees- clinical usage
disadvantages of agar?
requires specialist equipment
low tear strength
dimensionally unstable due to water content
What is the composition of alginate?
sodium of potassium salt of alginic acid 11-16%
cross linked gel when set
What is the source for cross linking setting reaction?
What controls working time of alginate?
How does sodium phosphate control working time?
limits availability of calcium ions
What are properties of alginate?
low viscosity- mucostatic
aqequate working time
sets by tissues first
no less than 3-5 mm thick