DOH110 W1 Flashcards
What is GIC Composition
Cement powder: Aluminosilicate glass (calcium or strontium) Acidic polymer: Polyalkenoicacid and water
What are the GIC 3 stages of setting reaction
Dissolution, Precipitation of Salts (Gelation/Hardening), Hydration of Salts
What is Dissolution
The surface layer of the glass is attacked by the polyacid to form a diffusion-based union between the two
What is Precipitation of Salts
Calcium/strontium and aluminium ions
bind to polyanionsat the carboxylate groups, Maturation takes place over 24h
What is Hydration of Salts
Maturation phase
of the progressive hydration of the matrix salts resulting in sharp improvement of the physical properties takes place up to several days
Describe the ability of GIC to bond to a tooth
GIC has the ability to bond chemically to mineralised tissues. Bonds better to enamel than dentine due to greater inorganic content
Describe GIC Chemical bonding to tooth structure
Diffusion-based adhesion.
Chemical bonding occurs through combined calcium/strontium phosphate/polyalkenoiatecrystalline structure acting as an interface between both enamel/dentine and the set material.
What is GIC Water balance
Auto cure Water in: immediately critical,
Water out: critical for 6m
What is RM GIC cements water balance
Water in: less critical for resin-modified and all others, Water out: critical for two weeks for all cements
Definition of impression material
An imprint of the teeth and adjacent structures for use in dentistry or mirror image
What is Phases 1 Alginate
1st sol◦The material is in a liquid or semiliquid form
What is Phases 2 Alginate
2nd gel◦The material is semisolid similar to a gelatindessert
Alginate Setting Characteristic phase 1
- (tri)sodium phosphate + calcium sulphate (allow working time)
Alginate Setting Characteristic phase 2
- remaining calcium sulphate + sodium/potassium alginate
Water? Alginate Properties
Water too hot reduces working time sets quicker Water too cold reverse effect
Powder &
Alginate Properties
Too much powder thick hard to mix too much water runs out of tray
What is Alginate Imbibition
water causes separation of aligned polysaccharide chains leading to swelling of impression
What is Alginate Synersis
Water lost by evaporation causing shrinkage
What is Alginate strenght
Poor mechanical strength and tears at low levels of stress
Reversible Hydrocolloids (agar)
Composition: Supplied in a gel
What is Reversible Hydrocolloids (agar) strenght
Properties: Poor mechanical strength and tears at low levels of stress.
What is Polysulphides
composition
Two-paste system dispensed from tubes:
What are Polysulphides Setting characteristics
chain extension and cross-linkage. Known as condensation polymerization reaction
Polyethers
Supplied as two pastes: base and catalyst
What is Polyethers Composition
Catalyst paste containing reaction initiator together with paste forming oils and fillers
What is the setting time for alginate
1.5 to 3min
