Glass Polyalkenoates Flashcards
Where are glass polyalkenoates derived from?
silicate and polycarboxylate cements
What are glass polyalkenoates used for?
Crowns and severely broken down teeth
What are the old contents of glass polyalkenoate cements?
zinc oxide powder
polyacrylic acid liquid
What is zinc oxide replaced with in the new formula?
glass polyalkenoate (glass ionomer)
What 3 forms do glass ionomer cements come in?
- powder and liquid
- powder and water
- encapsulated
What is a glass ionomer cement?
silicate glass and water soluble acidic polymer
When are glass ionomer cements used?
paediatric restorations
Why are glass ionomer cements the material of choice in patients with high caries risk?
fluoride release
What is the setting reaction for glass ionomer cements?
acid base reaction which results in a siliceous hydrogel, glass particle and water
What makes glass ionomer cements tooth coloured?
unreacted glass cores reflect the colour of tooth and transmit light
What releases fluoride in glass ionomer cements?
glass
What time is the initial set of glass ionomer cements?
3 minutes
What particle predominates during the initial set of glass ionomer cements and why?
Ca2+ - on the outer surface of glass particle and has smaller ionic radius
What time is the final set of glass ionomer cements?
24 hours
What particle predominates the final set of glass ionomer cements?
Al3+
Before the final set of glass ionomer cements, what must be avoided?
moisture
How do you protect the glass ionomer cement before the final set?
varnish or unfilled resin
- Vaseline as a lubricant when polishing
How can you reform a glass ionomer cement?
mix with water or dilute solution of the acid
What may increase the adhesion of glass ionomer cements?
tooth cleanser - citric acid
What makes a resin modified glass ionomer cement?
small addition of light-curing resin
What are the advantages of using RMGIC’s?
- varnish not required
- work faster
- expand in water
What is the advantage of RMGICs expanding in water?
helps seal cavity
How are RMGICs set?
light cure
What is HEMA?
an important component of RMGICs that enables resin and acid to co-exist in aqueous solution
How should RMGICs be applied?
rapidly in small increments
What is a giomer?
a modified glass ionomer
- fluoride release of GI
- resin composite aesthetic
What are the 2 giomer reaction types?
- surface reaction
- full reaction
What condition allows giomers to have greater fluoride release?
low pH
What are advantages of giomers?
- better aesthetic
- good mechanical properties
- finishing properties of resin composites
- fluoride release
