Glass Polyalkanoate Restorative Materials Flashcards
what were glass polyalkanoates previously referred to as?
glass ionomer
what 3 forms are glass polyalkanoates supplied as?
powder and liquid
powder mixed with water
encapsulated form
give the chemical composition of glass polyalkanoate powder in powder liquid supply
Sodium Aluminosilicate Glass with 20% CaF
give the chemical composition of glass polyalkanoate liquid in powder liquid supply
aqueous solution of acrylic/itaconic acid copolymer PLUS tartaric acid
what does the tartaric acid in the liquid composition of glass polyalkanoate control?
controls setting characteristics
what type of reaction is the setting reaction of glass polyalkanoate?
acid base
what is the powder composition of glass polyalkanoate powder in powder water supply
Sodium Aluminosilicate Glass with 20% CaF PLUS vacuum dried polyacid
clinically what must be carried out to obtain the final glass polyalkanoate material ready for restoration?
mixing with spatula or mixing machinery
why is froth likely to be seen after mechanical mixing of glass polyalkanoate?
high porosity of mixture after mechanical mixing
what part of the sodium aluminosilicate glass is left unreacted?
unreacted glass core
what does the unreacted glass core confer?
translucency
what does the set material of glass polyalkanoate consist of
glass particles
siliceous hydrogel
what is the hydrogel sensitive to?
moisture
what are the 2 phases in the setting reaction of polyalkanoate, what is setting and when do they occur?
initial set = Ca2+ ions set = first few minutes
final set = Al3+ ions set = 24 hours
what component of the glass particle is on the outer surface?
Ca2+
what component of the glass particle in the inner core?
Al3+
why do the Ca2+ ions set faster than the Al3+ ions?
calcium is more mobile
aluminium has more stringent stereochemical requirements for cross linking
as the material does not fully set for 24 hours and the material is sensitive to moisture, what steps must the clinician take to prevent the restoration form failing?
apply varnish or unfilled resin
apply vaseline when polishing
Note for safety of powder form of polyalkanoate?
always replace the lid immediately after use and avoid contact with eyes (patients and clinicians must be wearing eye protection)
what are the advantages of using glass polyalkanoate vs resin composite?
glass polyalkanoates have: inherent adhesion little shrinkage fluoride release biocompatible
what are the disadvantages of using glass polyalkanoate vs resin composite?
glass polyalkanoates are: brittle soluble not radiopaque (won't be obvious in X-ray) wear prone water sensitive slow set
what does RMGIC stand for?
resin modified glass ionomer cements
what is the modification of the resin composite in RMGICs?
aluminosilicate glass
what is the aim of the modification of resin composite in RMGICs?
to encourage fluoride release
modification of GI in RMGICs?
aluminosilicate glass is pre-reacted with polyacid to form a pre-reacted glass polyalkanoate complex
what are the 2 types of reaction used for pre-reacting the aluminosilicate glass in RMGICs?
surface reaction
full reaction
what are the 2 presentations RMGICs?
powder:liquid
encapsulated systems
what are the 3 setting reactions that occur on mixing of RMGICs?
acid base
light activation sets of resin polymerisation
chemical activators present then farthing curing
pros of RMGICs?
presences of resin means no varnish is required
finishing is possible immediately
cons of RMGICs?
must work quickly
